Help file for the Anaddb utility of the ABINIT package.
This file explains the use and i/o parameters needed for
the "Analysis of Derivative DataBase" code of the ABINIT package.
This code is able to compute interatomic force constants (hence its
name),
but also, more generally, many different physical properties
from databases containing derivatives of the total energy
(Derivative DataBase - DDB).
The user is not supposed to know how the Derivative
DataBase (DBB) has been generated. He/she should simply know what
material is described by the DDB he/she wants to use.
If he/she is interested in the generation of DDB, and wants to
know more about this
topic, he/she will read different help files of the ABINIT package,
related to the
main code, to the
response-function features of the main code,
to the merging code.
It will be easier to discover the
present file with the help of the tutorial, especially
the second lesson on response functions.
It is worthwhile to print this help file, for ease of reading.
Copyright (C) 1998-2008 ABINIT group (XG,DCA)
This file is distributed under the terms of the GNU General Public
License, see
~abinit/COPYING or
http://www.gnu.org/copyleft/gpl.txt .
For the initials of contributors, see
~abinit/doc/developers/contributors.txt .
Goto :
ABINIT home Page
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Suggested acknowledgments
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List of input variables
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Tutorial home page
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Bibliography
Help files :
New user's guide
|
Abinis (main)
|
Abinis (respfn)
|
Mrgddb
|
Anaddb
|
AIM (Bader)
|
Cut3D
|
Optic
|
Mrgscr
Content of the help file.
1. Introduction
In short, a Derivative DataBase contains a list of derivatives
of the total energy with respect to three kind of perturbations :
phonons, electric field and stresses. The present code analyses
the DDB, and directly gives properties of the material under
investigation, like phonon spectrum, frequency-dependent dielectric
tensor, thermal properties.
Given an input file (parameters described below),
the user must create a "files" file which lists names for the files
the job will require, including the main input file, the main output file,
the name of the DDB, and some other file names optionally used for selected capabilities of the code.
The files file (called for example ab.files) could look like:
anaddb.in
anaddb.out
ddb
band_eps
gkk
anaddb
In this example:
- the main input file is called "anaddb.in",
- the main output will be put into the file called "anaddb.out",
- the input DDB file is called "ddb",
- information to draw phonon band structures will go to band_eps
- the input GKK file is called "gkk" (used only for electron-phonon interactions)
- the base filename for output "anaddb" (used only for electron-phonon interactions)
Other examples are given in the ~abinit/test/v2 directory. The latter three filename information
is often not used by anaddb.
The maximal length
of names for the main input or output files is presently 132 characters.
The main executable file is called anaddb.
Supposing that the "files" file is called anaddb.files,
and that the executable is placed in your working directory, anaddb is run
interactively (in Unix) with the command
- anaddb < anaddb.files >& log
or, in the background, with the command
- anaddb < anaddb.files >& log &
where standard out and standard error are piped
to the log file called "log"
(piping the standard error, thanks to the '&' sign placed after '>'
is really important
for the analysis of eventual failures, when not due
to ABINIT, but to other sources, like disk full problem ...).
The user can specify
any names he/she wishes for any of these files.
Variations of the above commands
could be needed,
depending on the flavor of UNIX that is used on the platform
that is considered for running the code.
The syntax of the input file is strictly similar to the syntax of
the
main abinit input files : the file is parsed, keywords are identified,
comments are also identified. However, the multidataset mode is not
available.
We now list the input variables for the anaddb input file. In order
to discover them, it is easier to use the different lessons of the tutorial :
start with the second lesson on response functions,
then follow the lesson on elasticity and piezoelectricity,
the lesson on electron-phonon interaction, and
the lesson on non-linear properties.
If you are discovering this file with the help of the tutorial,
you can go back to the tutorial window.
2. The list of input variables.
Alphabetical list of input variables for ANADDB.
A.
alphon
asr
atftol
atifc
a2fsmear
B.
brav
C.
chneut
D.
dieflag
dipdip
dosdeltae
dossmear
dostol
E.
eivec
elaflag
elphflag
elphsmear
elph_fermie
enunit
ep_b_max
ep_b_min
F.
frmax
frmin
G.
gkk2exist
gkk2write
gkk_rptexist
gkk_rptwrite
gkqexist
gkqwrite
H.
I.
iatfix
iavfrq
ifatfix
ifcana
ifcflag
ifltransport
ifcout
instrflag
istrfix
J.
K.
L.
M.
mustar
N.
natfix
natifc
nchan
nfreq
ngqpt
ng2qpt
ngrids
nlflag
nph1l
nph2l
nqpath
nqshft
nsphere
nstrfix
ntemper
nwchan
O.
P.
phfrqexist
phfrqwrite
piezoflag
polflag
prtfsurf
prtmbm
prtdos
prtnest
Q.
qpath
qph1l
qph2l
q1shft
q2shft
R.
ramansr
relaxat
relaxstr
rfmeth
rifcsph
S.
selectz
symdynmat
T.
telphint
temperinc
tempermin
thmflag
thmtol
targetpol
U.
V.
vrsinddb
W.
X.
Y.
Z.
alphon
Mnemonics: ALign PHONon mode eigendisplacements
Characteristic:
Variable type: integer
Default: 0
In case alphon is set to 1, ANADDB will compute linear combinations of
the eigendisplacements of modes that are degenerate (twice or three times),
in order to align the mode effective charges along the cartesian axes.
This option is useful in the mode-by-mode decomposition of the
electrooptic tensor, and to compute
the Raman susceptibilities of individual phonon modes.
In case of uniaxial crystals, the z-axis should be chosen along the optical axis.
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| List of ANADDB input variables
asr
Mnemonics: Acoustic Sum Rule
Characteristic:
Variable type: integer
Default: 1 (was 0 before v5.3)
Govern the imposition of the Acoustic Sum Rule (ASR).
- 0 => no ASR for interatomic force constants is imposed.
- 1 or 2 => the ASR for interatomic force constants
is imposed by modifying the on-site interatomic force constants,
in a symmetric way (asr=2), or in the more general case,
unconstrained way (asr=1).
More detailed explanations : the total energy should be
invariant under translation of the crystal as a whole. This
would garantee that the three lowest phonon modes at Gamma
have zero frequency (Acoustic Sum Rule - ASR).
Unfortunately, the way the DDB is
generated (presence of a discrete grid of points for the
evaluation of the exchange-correlation potential and energy)
slightly breaks the translational invariance.
Well, in some pathological cases, the breaking can be rather
important.
Two quantities are affected : the interatomic forces
(or
dynamical matrices), and the effective charges.
The ASR for the effective charges is called the charge
neutrality sum rule, and will be dealt with by the variable
chneut.
The ASR for the interatomic forces can be restored,
by modifying the interatomic force of the atom on itself,
(called self-IFC), as soon as the dynamical matrix at Gamma
is known. This quantity
should be equal to minus the sum of all interatomic
forces generated by all others atoms (action-reaction law!),
which is determined by the dynamical matrix at Gamma.
So, if asr is non-zero, the correction to the self-force
will be determined, and the self-force will be imposed
to be consistent with the ASR.
This correction will work if IFCs are computed
(ifcflag/=0),
as well as if the IFCs are not computed
(ifcflag==0).
In both cases, the phonon frequencies will not be the same
as the ones determined by the output of abinit, RF case.
If you want to check that the DDB is correct, by comparing
phonon frequencies from abinit and anaddb, you should turn off
both asr and
chneut.
Until now, we have not explained the difference
between
asr=1 and asr=2. This is rather subtle.
In some local low-symmetry
cases (basically the effective charges should be anisotropic),
when the dipole-dipole contribution is evaluated and subtracted,
the ASR cannot be imposed without breaking the
symmetry of the on-site interatomic forces. That explains why two
options are given : the second case (asr=2, sym) does not
entirely impose the ASR, but simply the part that keeps the on-site
interatomic forces symmetric (which means that the acoustic frequencies
do not go to zero exactly), the first case (asr=1, asym)
imposes the ASR, but breaks the symmetry.
asr=2 is to be preferred for the analysis of the interatomic
force
constant in real space, while asr=1 should be used to get
the phonon band structure.
(NOTE : in order to confuse even more the situation,
it seems that the acoustic phonon frequencies generated by the code
for both the sym and asym options are exactly the same ...
likely due to an extra symmetrisation in the diagonalisation routine.
Of course, when
the matrix at Gamma has been generated from IFCs coming from dynamical
matrices none of which are Gamma, the breaking of the ASR is rather
severe. In order to clear the situation, one should use
a diagonalisation
routine for non-hermitian matrices. So, at the present status of
understanding, one should always use the asr=2 option ).
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| List of ANADDB input
variables
atftol
Mnemonics: ATomic Temperature Factor TOLerance
Characteristic:
Variable type: real
Default: 0.05
The relative tolerance on the atomic temperature
factors.
This number will determine when the series of channel widths
with which the DOS is calculated can be stopped, i.e.
the mean of the relative change going from one grid
to the next bigger is smaller than wtol2.
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variables
atifc
Mnemonics: AToms for IFC analysis
Characteristic:
Variable type: integer array atifc(
natifc)
Default: 0
The actual numbers of the atoms for which the
interatomic
force constant have to be written and eventually analysed.
WARNING : there will be an in-place change of meaning of atifc (this is
confusing,
and should be taken away in one future version - sorry for this).
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variables
a2fsmear
Mnemonics: Alpha2F SMEARing factor
Characteristic: ENERGY
Variable type: real
Default: 0.00002
Smearing width for the Eliashberg alpha^2F function
(similar to
a phonon DOS), which is sampled on a finite q and k grid. The Dirac
delta
functions in energy are replaced by Gaussians of width a2fsmear
(by default in Hartree).
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variables
brav
Mnemonics: BRAVais
Characteristic:
Variable type: integer
Default: 1
Allows to specify the Bravais lattice of the crystal,
in order to help to generate a grid of special q points.
- 1 => all the lattices (including FCC, BCC
and hexagonal)
- 2 => specific for Face Centered lattices
- 3 => specific for Body Centered lattices
- 4 => specific for the Hexagonal lattice
Note that in the latter case, the rprim of
the unit cell have to be 1.0 0.0 0.0 -.5 sqrt(3)/2 0.0 0.0 0.0 1.0
in order for the code to work properly.
Warning : the generation of q-points in anaddb is rather
old-fashioned, and should be replaced by routines used by
the main abinis code.
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chneut
Mnemonics: Integer for CHarge NEUTrality treatment
Characteristic:
Variable type: integer parameter
Default is 0.
Set the treatment of the Charge Neutrality requirement for
the effective charges.
- 0 => the dipole-dipole interaction is not handled separately
in the treatment of the interatomic forces. This option is available
for testing purposes or if effective charge and/or dielectric tensor is
not available in the derivative database. It gives results much less
accurate than dipdip=1.
- 1 => the dipole-dipole interaction is subtracted from the
dynamical matrices before Fourier transform, so that only the
short-range part is handled in real space. Of course, it is
reintroduced analytically when the phonon spectrum is interpolated, or
if the interatomic force constants have to be analysed in real space.
More detailed explanation : the sum of the effective charges
in the unit cell should be equal to zero. It is not the case
in the DDB, and this sum rule is sometimes strongly violated.
In particular, this will make the lowest frequencies at Gamma
non-zero. There is no "best" way of imposing the ASR
on effective charges. This is still under investigation.
It you have another idea of a way to impose it, please
call us, and we will try it ! Better yet, try it yourself
and tell us if it works and send us a copy !
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| List of ANADDB input variables
dieflag
Mnemonics: DIElectric FLAG
Characteristic:
Variable type: integer
Default: 0
Integer. Frequency-dependent dielectric tensor flag.
- 0 => No dielectric tensor is calculated.
- 1 => The frequency-dependent dielectric tensor is calculated.
The frequencies are defined by the
nfreq,
frmin,
frmax
variables. Also, the generalized Lyddane-Sachs-Teller
relation will be used as an independent check of the
dielectric tensor at zero frequency (this for the
directions defined in the phonon list 2.
See nph2l).
- 2 => Only the electronic dielectric tensor is calculated.
It corresponds to a zero-frequency homogeneous field,
with quenched atomic positions. For large band gap materials,
this quantity is measurable because the highest phonon
frequency is on the order of a few tenths of eV, and the
band gap is larger than 5eV.
- 3 => Compute and print the relaxed-ion dielectric tensor.
Requirements for preceding response-function DDB generation
run: electric-field and full atomic-displacement responses.
Set rfstrs = 1, 2, or 3 (preferably 3).
Set rfatpol and
rfdir to do a full calculation of
phonons at Q=0 (needed because the inverse of
force-constant tensor is required).
Note that the relaxed-ion dielectric tensor computed here can
also be obtained as the zero-frequency limit of the
frequency-dependent dielectric tensor using input variables
dieflag=1 and frmin=0.0. (The results obtained using these two
approaches should agree to good numerical precision.) The ability
to compute and print the static dielectric tensor here is provided
for completeness and consistency with the other tensor
quantities that are computed in this section of the code.
- 4 => Calculate dielectric tensor of both relaxed ion and
free stress.
We need information of internal strain and elastic tensor (relaxed ion)
in this computation. So please set:
elaflag=2,3,4 or 5 and
instrflag=1
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dipdip
Mnemonics: DIPole-DIPole interaction
Characteristic:
Variable type: integer
Default: 1
-
0 => the dipole-dipole interaction is not handled separately
in the treatment of the interatomic forces. This option
is available for testing purposes or if effective charge
and/or dielectric tensor is not available in the derivative
database. It gives results much less accurate than dipdip=1.
-
1 => the dipole-dipole interaction is subtracted from the dynamical
matrices before Fourier transform, so that only the short-range
part is handled in real space. Of course, it is reintroduced
analytically when the phonon spectrum is interpolated, or if
the interatomic force constants have to be analysed in real space.
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| List of ANADDB input variables
dosdeltae
Mnemonics: DOS DELTA in Energy
Characteristic:
Variable type: real
Default: 4.5E-06 Hartree = 1 cm-1
The input variable dosdeltae is used to define the step of the frequency grid used to
calculate the phonon density of states when prtdos=1.
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dossmear
Mnemonics: DOS SMEARing value
Characteristic: Energy
Variable type: real
Default: 4.5E-05 Hartree = 10 cm-1
dossmear defines the gaussian broadening used to calculate the phonon density
of states when prtdos=1.
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dostol
Mnemonics: DOS TOLerance
Characteristic:
Variable type: real
Default: 0.25
The relative tolerance on the phonon density of state.
This number will determine when the series of grids
with which the DOS is calculated can be stopped, i.e.
the mean of the relative change going from one grid
to the next bigger is smaller than dostol.
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eivec
Mnemonics: EIgenVECtors
Characteristic:
Variable type: integer
Default: 0
- 0 => do not write the phonon eigenvectors;
- 1 or 2 => write the phonon eigenvectors;
- 3 => write the phonon eigenvectors, in the lwf-formatted file;
- 4 => generate output files for band2eps (drawing tool for the phonon band structure);
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elaflag
Mnemonics: ELAstic tensor FLAG
Characteristic:
Variable type: integer
Default: 0
Flag for calculation of elastic and compliance tensors
- 0 => No elastic or compliance tensor will be calculated.
- 1 => Only clamped-ion elastic and compliance tensors will be
calculated.
Requirements for preceding response-function DDB generation
run: Strain perturbation.
Set rfstrs to 1, 2, or 3.
Note that rfstrs=3 is recommended so that responses to
both uniaxial and shear strains will be computed.
- 2 => Both relaxed- and clamped-ion elastic and compliance tensor
will be calculated, but only the relaxed-ion quantities
will be printed.
The input variable instrflag
should also be set to 1, because
the internal-strain tensor is needed to compute the relaxed-ion
corrections. Requirements for preceding response-function DDB
generation run: Strain and atomic-displacement responses at Q=0.
Set rfstrs = 1, 2, or 3 (preferably 3).
Set rfatpol and
rfdir to do a full calculation of
phonons at Q=0 (needed because the inverse of
force-constant tensor is required).
- 3 => Both relaxed and clamped-ion elastic and compliance tensors
will be printed out.
The input variable instrflag
should also be set to 1.
Requirements for preceeding response-function DDB generation
run: Same as for elaflag=2.
- 4 => Calculate the elastic and compliance tensors (relaxed ion)
at fixed displacement field, the relaxed-ion tensors at fixed
electric field will be printed out too, for comparison.
When elaflag=4, we need the information of internal strain and
relaxed-ion dielectric tensor to build the whole tensor, so
we need set instrflag=1 and
dieflag=3 or 4 .
- 5 => Calculate the relaxed ion elastic and compliance tensors, considering
the stress left inside cell. At the same time, bare relaxed ion tensors
will still be printed out for comparison.
In this calculation, stress tensor is needed to compute the correction
term, so one supposed to merge the first order derivative data base (DDB file)
with the second order derivative data base (DDB file) into a new DDB file, which
can contain both information. And the program will also check for the users.
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| List of ANADDB input variables
elphflag
Mnemonics: ELectron-PHonon FLAG
Characteristic:
Variable type: integer
Default: 0
If elphflag is 1, anaddb performs an analysis of the electron-phonon coupling.
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elphsmear
Mnemonics: ELectron-PHonon SMEARing factor
Characteristic: ENERGY
Variable type: real
Default: 0.01 Hartree
Smearing width for the Fermi surface integration (in Hartree by default).
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elph_fermie
Mnemonics: ELectron-PHonon FERMI Energy
Characteristic: ENERGY
Variable type: real
Default: 0.0
If non-zero, will fix artificially the value of the Fermi energy
(e.g. for semiconductors), in the electron-phonon case
(elphflag=1).
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enunit
Mnemonics: ENergy UNITs
Characteristic:
Variable type: integer
Default: 0
Give the energy for the phonon frequency output
(in the output file, not in the console log file, for
which Hartree units are used).
- 0 => Hartree and cm-1;
- 1 => meV and Thz;
- 2 => Hartree, cm-1, meV, Thz, and Kelvin.
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ep_b_max
Mnemonics: (TO BE COMPLETED)
Characteristic:
Variable type: integer
Default: 0
TO BE COMPLETED
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ep_b_min
Mnemonics: (TO BE COMPLETED)
Characteristic:
Variable type: integer
Default: 0
TO BE COMPLETED
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frmax
Mnemonics: FRequency : MAXimum
Characteristic:
Variable type: real number
Default: 10.0
Value of the largest frequency for the
frequency-dependent dielectric tensor, in Hartree.
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| List of ANADDB input variables
frmin
Mnemonics: FRequency : MINimum
Characteristic:
Variable type: real number
Default: 0.0
Value of the lowest frequency for the
frequency-dependent dielectric tensor, in Hartree.
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| List of ANADDB input variables
gkk2exist
Mnemonics: GKK double fine grid EXIST on disk
Characteristic:
Variable type: integer
Default: 0
Flag to read in electron-phonon matrix elements on double full fine kpoint
grid. If set to 1 the full anisotropic matrix elements (not used currently) are
presumed to be on disk in a file called gkk2file.
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| List of ANADDB input variables
gkk2write
Mnemonics: GKK double fine grid to be WRITtEn to disk
Characteristic:
Variable type: integer
Default: 0
Flag to write out gkk2 matrix elements to disk file named gkk2file. In
subsequent runs set gkk2exist to 1 to skip their re-generation and read in from
file.
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| List of ANADDB input variables
gkk_rptexist
Mnemonics: GKK on Real space PoinTs EXIST on disk
Characteristic:
Variable type: integer
Default: 0
Flag to read in real space matrix elements of the electron-phonon coupling. If
set to 1 the real space elements (not used currently) are presumed to be on
disk in a file called gkk_rpt_file.
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| List of ANADDB input variables
gkk_rptwrite
Mnemonics: GKK on Real space PoinTs to be WRITtEn to disk
Characteristic:
Variable type: integer
Default: 0
Flag to write out real space electron-phonon matrix elements to disk. In
subsequent runs set gkk_rptexist to 1 to skip their re-generation.
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| List of ANADDB input variables
gkqexist
Mnemonics: GKk for input Q grid EXIST on disk
Characteristic:
Variable type: integer
Default: 0
Flag to read in reciprocal space matrix elements from disk file gkqfile. The
linewidths and 1D electron-phonon quantities can be calculated directly after
the FFT to real space.
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| List of ANADDB input variables
gkqwrite
Mnemonics: GKk for input Q grid to be WRITtEn to disk
Characteristic:
Variable type: integer
Default: 0
Flag to write out the reciprocal space matrix elements to a disk file named
gkqfile. In subsequent runs set gkqexist to 1 to skip their re-generation.
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phfrqexist
Mnemonics: PHonon FReQuencies EXIST on disk
Characteristic:
Variable type: integer
Default: 0
Flag to read in phonon frequencies on fine electron-phonon grid from disk file
phfrqfile, which is identical to the kpoint grid (minus any shift). Only used
furing the full anisotropic treatment of the elphon quantities (see gkk2exist
gkk2write), which are not functional yet.
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| List of ANADDB input variables
phfrqwrite
Mnemonics: PHonon FReQuencies to be WRITtEn to disk
Characteristic:
Variable type: integer
Default: 0
Flag to write out phonon frequencies to disk file phfrqfile. In subsequent runs
set phfrqexist to 1 to skip their re-generation.
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| List of ANADDB input variables
iavfrq
Mnemonics: Integer for the printing of AVerage FReQuency
Characteristic:
Variable type: integer
Default: 0
Used only when thmflag=1.
When this flag is set to 1, the "average frequency" is printed out (as a
function of temperature, with phonon internal energy, free energy, entropy, ...).
The average frequency is defined as:
Omega_average = Sum_over_q_and_i [Cv_iq Omega_iq]/Cv
where
- Omega_iq is the frequency of the ith mode for q-point q
- Cv is the specific heat
- Cv_iq is the contribution to the specific heat of the ith mode for q-point q
The "average frequency" can be used to have an estimation of the average
Gruneisen parameter: Gamma_average=-d(log(Omega_average))/d(log(V)).
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iatfix
Mnemonics: Indices of the AToms that are FIXed
Characteristic:
Variable type: integer array (1:natfix)
Default: 0
Indices of the atoms that are fixed during a structural relaxation at constrained polarization.
See polflag.
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| List of ANADDB input variables
ifcana
Mnemonics: IFC ANAlysis
Characteristic:
Variable type: integer
Default: 0
- 0 => no analysis of interatomic force constants;
- 1 => analysis of interatomic force constants.
If the analysis is activated, one get the
trace of the matrices between pairs of atoms,
if dipdip is 1,
get also the trace of the short-range
and electrostatic part, and
calculate the ratio with the full matrice;
then define a local coordinate reference (using
the next-neighbour coordinates), and express
the interatomic force constant matrix between
pairs of atoms in that local coordinate reference
(the first vector is along the bond; the second
vector is along the perpendicular force exerted
on the generic atom by a longitudinal displacement
of the neighbouring atom - in case it does not vanish;
the third vector is perpendicular to the two other)
also calculate ratios with respect to the
longitudinal force constant ( the (1,1) element of
the matrix in local coordinates).
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| List of ANADDB input variables
ifcflag
Mnemonics: Interatomic Force Constants FLAG
Characteristic:
Variable type: integer
Default: 0
- 0 => do all calculations directly from the DDB, without the
use of the interatomic force constant.
- 1 => calculate and use the interatomic force constants
for interpolating the phonon spectrum and dynamical
matrices at every q wavevector, and eventually analyse
the interatomic force constants, according to the
informations given by
atifc,
dipdip,
ifcana,
ifcout,
natifc,
nsphere,
rifcsph.
More detailed explanations : if the dynamical matrices
are known on a regular set of wavevectors, they
can be used to get the interatomic forces, which are simply
their Fourier transform. When non-analyticities
can been removed by the use of effective charge at Gamma
(option offered by putting
dipdip to 1),
the interatomic forces are known to decay rather fast (in real space).
The interatomic forces generated from a small set of
dynamical matrices
could be of sufficient range to allow
the remaining interatomic forces to be neglected.
This gives a practical way to interpolate the content
of a small set of dynamical matrices, because dynamical
matrices can everywhere be generated starting from this
set of interatomic force constants. It is suggested to
always use ifcflag=1. The ifcflag=0 option
is available for
checking purpose, and if there is not enough information
in the DDB.
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ifcout
Mnemonics: IFC OUTput
Characteristic:
Variable type: integer
Default: 0
For each atom in the list
atifc (generic atoms),
ifcout give the number
of neighbouring atoms for which the ifc's will be
output (written) and eventually analysed. The
neighbouring atoms are selected by decreasing distance with respect to
the generic atom.
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ifltransport
Mnemonics: IFLag for TRANSPORT
Characteristic:
Variable type: integer
Default: 0
if ifltransport=1 anaddb calculates the transport
properties: electrical and thermal resistivities from electron-phonon
interactions (needs elphflag = 1)
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instrflag
Mnemonics: INternal STRain FLAG
Characteristic:
Variable type: integer
Default: 0
Internal strain tensor flag.
- 0 => No internal-strain calculation.
- 1 => Print out both force-response and displacement-response
internal-strain tensor.
Requirements for preceding response-function DDB generation
run: Strain and full atomic-displacement responses.
Set rfstrs = 1, 2, or 3 (preferably 3).
Set rfatpol and
rfdir to do a full calculation of
phonons at Q=0.
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istrfix
Mnemonics: Index of STRain FIXed
Characteristic:
Variable type: integer array istrfix(1:nstrfix)
Default: 0
Indices of the elements of the strain tensor that are fixed during a structural relaxation
at constrained polarisation :
- 0 => No elastic or compliance tensor will be calculated.
- 1 => Only clamped-ion elastic and compliance tensors will be
calculated. Requirements for preceding response-function DDB generation
run: Strain perturbation. Set rfstrs to 1, 2, or 3.
Note that rfstrs=3
is recommended so that responses to both uniaxial and shear strains
will be computed.
- 2 => Both relaxed- and clamped-ion elastic and compliance
tensor will be calculated, but only the relaxed-ion quantities will be
printed. The input variable instrflag
should also be set to 1, because the internal-strain tensor is needed
to compute the relaxed-ion corrections. Requirements for preceding
response-function DDB generation run: Strain and atomic-displacement
responses at Q=0. Set rfstrs
= 1, 2, or 3 (preferably 3). Set rfatpolrfatpol and rfdir to do a full
calculation of phonons at Q=0 (needed because the inverse of
force-constant tensor is required).
- 3 => Both relaxed and clamped-ion elastic and compliance
tensors will be printed out. The input variable instrflag should also be set to
1. Requirements for preceeding response-function DDB generation run:
Same as for elaflag=2'.
- 4 => Calculate the elastic and compliance tensors (relaxed
ion) at fixed displacement field, the relaxed-ion tensors at fixed
electric field will be printed out too, for comparison. When elaflag=4,
we need the information of internal strain and relaxed-ion dielectric
tensor to build the whole tensor, so we need set instrflag=1 and dieflag=3 or 4 .
- 5 => Calculate the relaxed ion elastic and compliance tensors,
considering the stress left inside cell. At the same time, bare relaxed
ion tensors will still be printed out for comparison. In this
calculation, stress tensor is needed to compute the correction term, so
one supposed to merge the first order derivative data base (DDB file)
with the second order derivative data base (DDB file) into a new DDB
file, which can contain both information. And the program will also
check for the users.
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| List of ANADDB input
variables
elphflag
Mnemonics: ELectron-PHonon FLAG
Characteristic:
Variable type: integer
Default: 0
If elphflag is 1, anaddb performs an analysis
of the electron-phonon coupling.
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variables
elphsmear
Mnemonics: ELectron-PHonon SMEARing factor
Characteristic: ENERGY
Variable type: real
Default: 0.01 Hartree
Smearing width for the Fermi surface integration (in
Hartree by default).
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variables
elph_fermie
Mnemonics: ELectron-PHonon FERMI Energy
Characteristic: ENERGY
Variable type: real
Default: 0.0
If non-zero, will fix artificially the value of the
Fermi energy
(e.g. for semiconductors), in the electron-phonon case (elphflag=1).
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| List of ANADDB input
variables
enunit
Mnemonics: ENergy UNITs
Characteristic:
Variable type: integer
Default: 0
Give the energy for the phonon frequency output
(in the output file, not in the console log file, for which Hartree
units are used).
- 0 => Hartree and cm-1;
- 1 => meV and Thz;
- 2 => Hartree, cm-1, meV, Thz, and Kelvin.
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| List of ANADDB input
variables
frmax
Mnemonics: FRequency : MAXimum
Characteristic:
Variable type: real number
Default: 10.0
Value of the largest frequency for the
frequency-dependent dielectric tensor, in Hartree.
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variables
frmin
Mnemonics: FRequency : MINimum
Characteristic:
Variable type: real number
Default: 0.0
Value of the lowest frequency for the
frequency-dependent dielectric tensor, in Hartree.
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variables
gkk2exist
Mnemonics: GKK double fine grid EXIST on disk
Characteristic:
Variable type: integer
Default: 0
Flag to read in electron-phonon matrix elements on
double full fine kpoint
grid. If set to 1 the full anisotropic matrix elements (not used
currently) are
presumed to be on disk in a file called gkk2file.
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variables
gkk2write
Mnemonics: GKK double fine grid to be WRITtEn to
disk
Characteristic:
Variable type: integer
Default: 0
Flag to write out gkk2 matrix elements to disk file
named gkk2file. In
subsequent runs set gkk2exist to 1 to skip their re-generation and read
in from
file.
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variables
gkk_rptexist
Mnemonics: GKK on Real space PoinTs EXIST on disk
Characteristic:
Variable type: integer
Default: 0
Flag to read in real space matrix elements of the
electron-phonon coupling. If
set to 1 the real space elements (not used currently) are presumed to
be on
disk in a file called gkk_rpt_file.
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variables
gkk_rptwrite
Mnemonics: GKK on Real space PoinTs to be WRITtEn
to disk
Characteristic:
Variable type: integer
Default: 0
Flag to write out real space electron-phonon matrix
elements to disk. In
subsequent runs set gkk_rptexist to 1 to skip their re-generation.
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variables
gkqexist
Mnemonics: GKk for input Q grid EXIST on disk
Characteristic:
Variable type: integer
Default: 0
Flag to read in reciprocal space matrix elements from
disk file gkqfile. The
linewidths and 1D electron-phonon quantities can be calculated directly
after
the FFT to real space.
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variables
gkqwrite
Mnemonics: GKk for input Q grid to be WRITtEn to
disk
Characteristic:
Variable type: integer
Default: 0
Flag to write out the reciprocal space matrix elements
to a disk file named
gkqfile. In subsequent runs set gkqexist to 1 to skip their
re-generation.
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variables
phfrqexist
Mnemonics: PHonon FReQuencies EXIST on disk
Characteristic:
Variable type: integer
Default: 0
Flag to read in phonon frequencies on fine
electron-phonon grid from disk file
phfrqfile, which is identical to the kpoint grid (minus any shift).
Only used
furing the full anisotropic treatment of the elphon quantities (see
gkk2exist
gkk2write), which are not functional yet.
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| List of ANADDB input
variables
phfrqwrite
Mnemonics: PHonon FReQuencies to be WRITtEn to
disk
Characteristic:
Variable type: integer
Default: 0
Flag to write out phonon frequencies to disk file
phfrqfile. In subsequent runs
set phfrqexist to 1 to skip their re-generation.
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variables
iatfix
Mnemonics: Indices of the AToms that are FIXed
Characteristic:
Variable type: integer array (1:natfix)
Default: 0
Indices of the atoms that are fixed during a structural
relaxation at constrained polarization.
See polflag.
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variables
ifcana
Mnemonics: IFC ANAlysis
Characteristic:
Variable type: integer
Default: 0
- 0 => no analysis of interatomic force
constants;
- 1 => analysis of interatomic force constants.
If the analysis is activated, one get the
trace of the matrices between pairs of atoms,
if dipdip is 1, get also the
trace of the short-range
and electrostatic part, and
calculate the ratio with the full matrice;
then define a local coordinate reference (using
the next-neighbour coordinates), and express
the interatomic force constant matrix between
pairs of atoms in that local coordinate reference
(the first vector is along the bond; the second
vector is along the perpendicular force exerted on the generic atom by
a longitudinal displacement
of the neighbouring atom - in case it does not vanish;
the third vector is perpendicular to the two other)
also calculate ratios with respect to the longitudinal force constant (
the (1,1) element of
the matrix in local coordinates).
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variables
ifcflag
Mnemonics: Interatomic Force Constants FLAG
Characteristic:
Variable type: integer
Default: 0
- 0 => do all calculations directly from the DDB, without the
use of the interatomic force constant.
- 1 => calculate and use the interatomic force constants for
interpolating the phonon spectrum and dynamical matrices at every q
wavevector, and eventually analyse the interatomic force constants,
according to the informations given by
atifc,
dipdip,
ifcana,
ifcout,
natifc,
nsphere,
rifcsph.
More detailed explanations : if the dynamical matrices are known on a
regular set of wavevectors, they can be used to get the interatomic
forces, which are simply their Fourier transform. When
non-analyticities can been removed by the use of effective charge at
Gamma (option offered by putting
dipdip to 1), the interatomic
forces are known to decay rather fast (in real space). The interatomic
forces generated from a small set of dynamical matrices could be of
sufficient range to allow the remaining interatomic forces to be
neglected. This gives a practical way to interpolate the content of a
small set of dynamical matrices, because dynamical matrices can
everywhere be generated starting from this set of interatomic force
constants. It is suggested to always use ifcflag=1. The ifcflag=0
option
is available for
checking purpose, and if there is not enough information
in the DDB.
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variables
ifcout
Mnemonics: IFC OUTput
Characteristic:
Variable type: integer
Default: 0
For each atom in the list atifc (generic atoms),
ifcout give the number
of neighbouring atoms for which the ifc's will be
output (written) and eventually analysed. The
neighbouring atoms are selected by decreasing distance with respect to
the generic atom.
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variables
ifltransport
Mnemonics: IFLag for TRANSPORT
Characteristic:
Variable type: integer
Default: 0
if ifltransport=1 anaddb calculates the transport
properties: electrical and thermal resistivities from electron-phonon
interactions (needs elphflag = 1)
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variables
instrflag
Mnemonics: INternal STRain FLAG
Characteristic:
Variable type: integer
Default: 0
Internal strain tensor flag.
- 0 => No internal-strain calculation.
- 1 => Print out both force-response and displacement-response
internal-strain tensor. Requirements for preceding response-function
DDB generation run: Strain and full atomic-displacement responses. Set rfstrs = 1, 2, or 3
(preferably 3). Set rfatpol
and rfdir to do a
full calculation of phonons at Q=0.
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variables
istrfix
Mnemonics: Index of STRain FIXed
Characteristic:
Variable type: integer array istrfix(1:nstrfix)
Default: 0
Indices of the elements of the strain tensor that are
fixed during a structural relaxation
at constrained polarisation :
- 1 -> xx
- 2 -> yy
- 3 -> zz
- 4 -> yz & zy
- 5 -> xz & zx
- 6 -> xy & yx
See polflag.
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variables
mustar
Mnemonics: MU STAR
Characteristic:
Variable type: real
Default: 0.1
Average electron-electron interaction strength, for the
computation of the
superconducting Tc using Mc-Millan's formula.
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variables
natfix
Mnemonics: Number of AToms FIXed
Characteristic:
Variable type: integer
Default: 0
Number of atoms that are fixed during a structural
optimisation at constrained polarization.
See polflag.
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variables
natifc
Mnemonics: Number of AToms for IFC analysis
Characteristic:
Variable type: integer
Default: 0
Give the number of atoms for which ifc's are written
and
eventually analysed. The list of these atoms is provided
by atifc
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nchan
Mnemonics: Number of CHANnels
Characteristic:
Variable type: integer
Default: 800
The number of channels of width 1 cm-1
used in calculating the
phonon density of states through the histogram method,
or, equivalently, the largest frequency sampled.
The first channel begins at 0.
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nfreq
Mnemonics: Number of FREQuencies
Characteristic:
Variable type: integer
Default: 1
Number of frequencies wanted for the
frequency-dependent dielectric tensor. Should be positive.
See dieflag.
The code will take nfreq equidistant values from
frmin to
frmax.
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| List of ANADDB input variables
ngqpt
Mnemonics: Number of Grids points for Q PoinTs
Characteristic:
Variable type: integer array ngqpt(3)
Default: 3*0 (will not work)
The Monkhorst-Pack grid linear dimensions, for the DDB (coarse grid).
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ng2qpt
Mnemonics: Number of Grids points for Q PoinTs (grid 2)
Characteristic:
Variable type: integer array ng2qpt(3)
Default: 3*0 (will not work)
The Monkhorst-Pack grid linear dimensions, for the finer of the
series of fine grids. Used for the integration
of thermodynamical functions (Bose-Einstein distribution)
or for the DOS.
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variables
ngrids
Mnemonics: Number of GRIDS
Characteristic:
Variable type: integer
Default: 4
This number define the series of grids that will be
used
for the estimation of the phonon DOS. The coarsest will be
tried first, then the next, ... then the one
described by
ng2qpt.
The intermediate grids are defined
for igrid=1... ngrids,
by the numbers ngqpt_igrid(ii)=(ng2qpt(ii)*igrid)/ngrids
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| List of ANADDB input variables
nlflag
Mnemonics: Non-Linear FLAG
Characteristic:
Variable type: integer
Default: 0
Non-linear properties flag.
- 0 => do not compute non-linear properties ;
- 1 => the electrooptic tensor, Raman susceptibilities and non-linear optical
susceptibilities are calculated;
- 2 => only the non-linear optical susceptibilities and first-order
changes of the dielectric tensor induced by an atomic displacement are calculated;
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| List of ANADDB input variables
nph1l
Mnemonics: Number of PHonons in List 1
Characteristic:
Variable type: integer
Default: 0
Integer. The number of wavevectors in phonon list 1. The actual
values of these wavevectors will be specified by
qph1l
The dynamical matrix for these wavevectors, obtained
either directly from the DDB - if
ifcflag=0 - or through
the interatomic forces interpolation - if
ifcflag=1 -),
will be diagonalized, and the corresponding eigenfrequencies
will be printed.
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| List of ANADDB input variables
nph2l
Mnemonics: Number of PHonons in List 2
Characteristic:
Variable type: integer
Default: 0
The number of wavevectors in phonon list 2. The actual
values of these wavevectors will be specified in the following.
these are actually all wavectors at Gamma, but obtained
by a limit along a different direction in the Brillouin-zone.
It is important to note that non-analyticities in the
dynamical matrices are present at Gamma, due to the
long-range Coulomb forces. So, going to Gamma along different
directions can give different results.
The wavevectors in list 2 will be used to :
- generate and diagonalize dynamical matrix, and print the
corresponding eigenvalues.
- calculate the generalized Lyddane-Sachs-Teller relation.
Note that if the three first numbers are zero, then
the code will do a calculation at Gamma without
non-analyticities.
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| List of ANADDB input variables
nqpath
Mnemonics: Number of Q wavevectors defining a PATH
Characteristic:
Variable type: integer
Default: 0
Number of q-points in the array qpath
defining the path along which the phonon band structure and phonon linewidths
are interpolated.
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| List of ANADDB input variables
nqshft
Mnemonics: Number of Q SHiFTs
Characteristic:
Variable type: integer
Default: 1
The number of vector shifts of the simple Monkhorst and
Pack grid, needed to generate the coarse grid of q points
(for the series of fine grids, the number of shifts it is always taken to be 1).
Usually, put it to 1.
Use 2 if BCC sampling (Warning : not BCC lattice, BCC *sampling*),
and 4 for FCC sampling (Warning : not FCC lattice, FCC *sampling*).
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variables
nsphere
Mnemonics: Number of atoms in SPHERe
Characteristic:
Variable type: integer
Default: 0
Number of atoms included in the cut-off sphere for
interatomic force constant, see also the alternative rifcsph.
If nsphere= 0 : maximum extent allowed by the grid .
This number defines the atoms for which the
short range part of the interatomic force constants, after
imposition of the acoustic sum rule, will not be put to zero.
This option is available for testing purposes
(evaluate the range of the interatomic force constants), because
the acoustic sum rule will be violated if some atoms are no more
included in the inverse Fourier Transform.
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variables
nstrfix
Mnemonics: Number of STRain components FIXed
Characteristic:
Variable type: integer
Default: 0
Number of strain component that are fixed during a
structural optimisation at constrained polarization.
See polflag.
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variables
ntemper
Mnemonics: Number of TEMPERatures
Characteristic:
Variable type: integer
Default: 400
Number of temperatures at which the thermodynamical
quantities have to be evaluated
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| List of ANADDB input variables
nwchan
Mnemonics: Number of Widths of CHANnels
Characteristic:
Variable type: integer
Default: 10
Integer. The width of the largest channel
used to sample the frequencies.
The code will generate different sets of channels,
with decreasing widths (by step of 1 cm-1), from
this channel width to 1, eventually. It considers to
have converged when the convergence criterion based on
dostol and
thmtol have been fulfilled.
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variables
piezoflag
Mnemonics: PIEZOelectric tensor FLAG
Characteristic:
Variable type: integer
Default: 0
Flag for calculation of piezoelectric tensors
- 0 => No piezoelectric tensor will be calculated.
- 1 => Only the clamped-ion piezoelectric tensor is computed and
printed. Requirements for preceding response-function DDB generation
run: Strain and electric-field responses. For the electric-field part,
one needs results from a prior 'ddk perturbation' run. Note that even
if only a limited number of piezoelectric tensor terms are wanted (as
determined by rfstrs and rfdir in this calculation) it is necessary to
set rfdir = 1 1 1 in the d/dk calculation for most structures. The only
obvious exception to this requirement is cases in which the primitive
lattice vectors are all aligned with the cartesian axes. The code will
omit terms in the output piezoelectric tensor for which the available
d/dk set is incomplete. Thus: Set rfstrs to 1, 2, or 3i
(preferably 3)
- 2 => Both relaxed- and clamped-ion elastic and compliance
tensor will be calculated, but only the relaxed-ion quantities will be
printed. The input variable instrflag
should also be set to 1, because the internal-strain tensor is needed
to compute the relaxed-ion corrections. Requirements for preceding
response-function DDB generation run: Strain, electric-field and full
atomic-displacement responses at Q=0. Set rfstrs = 1, 2, or 3
(preferably 3). Set rfelfd
= 3. Set rfatpol
and rfdir to do a
full calculation of phonons at Q=0 (needed because the inverse of
force-constant tensor is required).
- 3 => Both relaxed and clamped-ion piezoelectric tensors will
be printed out. The input variable instrflag
should also be set to 1. Requirements for preceding response-function
DDB generation run: Same as for piezoflag=2.
- 4 => Calculate the piezoelectric d tensor (relaxed ion). In
order to calculate the piezoelectric d tensor, we need information of
internal strain and elastic tensor (relaxed ion). So we should set elaflag= 2,3,4, or 5 and instrflag=1. The subroutine will
also do a check for you, and print warning message without stopping
even if flags were not correctly set.
- 5 => Calculate the piezoelectric g tensor (relaxed ion). In
this computation, we need information of internal strain, elastic
tensor (relaxed ion) and dielectric tensor (relaxed ion). So we should
set: instrflag=1, elaflag=2,3,4 or 5, dieflag=3 or 4. The subroutine
will also do a check for you, and print warning message without
stopping even if flags were not correctly set.
- 6 => Calculate the piezoelectric h tensor (relaxed ion). In
this calculation, we need information of internal strain and dielectric
tensor (relaxed ion). So we need set: instrflag=1 and dieflag=3 or 4. The subroutine
will also do a check for you, and print warning message without
stopping even if flags were not correctly set.
- 7 => calculate all the possible piezoelectric tensors,
including e (clamped and relaxed ion), d, g and h tensors. The flags
should be set to satisfy the above rules from 1 to 6.
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| List of ANADDB input variables
piezoflag
Mnemonics: PIEZOelectric tensor FLAG
Characteristic:
Variable type: integer
Default: 0
Flag for calculation of piezoelectric tensors
- 0 => No piezoelectric tensor will be calculated.
- 1 => Only the clamped-ion piezoelectric tensor is computed and
printed. Requirements for preceding response-function DDB generation
run: Strain and electric-field responses. For the
electric-field part, one needs results from a prior 'ddk
perturbation' run. Note that even if only a limited number
of piezoelectric tensor terms are wanted (as determined by
rfstrs and rfdir in this calculation) it is necessary to set
rfdir = 1 1 1 in the d/dk calculation for most structures.
The only obvious exception to this requirement is cases in
which the primitive lattice vectors are all aligned with the
cartesian axes. The code will omit terms in the output
piezoelectric tensor for which the available d/dk set is
incomplete. Thus:
Set rfstrs to 1, 2, or 3i (preferably 3)
- 2 => Both relaxed- and clamped-ion elastic and compliance tensor
will be calculated, but only the relaxed-ion quantities
will be printed.
The input variable instrflag
should also be set to 1, because
the internal-strain tensor is needed to compute the relaxed-ion
corrections. Requirements for preceding response-function DDB
generation run: Strain, electric-field and full atomic-displacement responses at Q=0.
Set rfstrs = 1, 2, or 3 (preferably 3).
Set rfelfd = 3.
Set rfatpol and
rfdir to do a full calculation of
phonons at Q=0 (needed because the inverse of
force-constant tensor is required).
- 3 => Both relaxed and clamped-ion piezoelectric tensors
will be printed out.
The input variable instrflag
should also be set to 1.
Requirements for preceding response-function DDB generation
run: Same as for piezoflag=2.
- 4 => Calculate the piezoelectric d tensor (relaxed ion).
In order to calculate the piezoelectric d tensor, we need information
of internal strain and elastic tensor (relaxed ion). So we should set
elaflag= 2,3,4, or 5 and
instrflag=1. The subroutine will also do a
check for you, and print warning message without stopping even if
flags were not correctly set.
- 5 => Calculate the piezoelectric g tensor (relaxed ion).
In this computation, we need information of internal strain,
elastic tensor (relaxed ion) and dielectric tensor (relaxed ion).
So we should set:
instrflag=1,
elaflag=2,3,4 or 5,
dieflag=3 or 4.
The subroutine will also do a check for you, and print warning message
without stopping even if flags were not correctly set.
- 6 => Calculate the piezoelectric h tensor (relaxed ion).
In this calculation, we need information of internal strain and
dielectric tensor (relaxed ion). So we need set:
instrflag=1
and
dieflag=3 or 4.
The subroutine will also do a check for you,
and print warning message without stopping even if flags were not
correctly set.
- 7 => calculate all the possible piezoelectric tensors, including
e (clamped and relaxed ion), d, g and h tensors.
The flags should be set to satisfy the above rules from 1 to 6.
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| List of ANADDB input variables
polflag
Mnemonics: POLarization FLAG
Characteristic:
Variable type: integer
Default: 0
If activated, compute polarization in cartesian coordinates,
and update lattice constants and atomic positions in order to perform a structural
optimization at constrained polarization.
More detailed explanation : ANADDB can use the formalism described in
Na Sai et al, PRB 66, 104108 (2002), to perform structural relaxations
under the constraint that the polarization is equal to a value specified by the
input variable targetpol.
The user starts from a given configurationof a crystal and performs
a ground-state calculation of the Hellman-Feynman forces and stresses
and the Berry phase polarization as
well as a linear response calculation of the whole matrix of
second-order energy derivatives with respect to atomic displacement,
strains and electric field.
In case polflag=1, ANADDB solves the linear system of equations
(13)
of the Na Sai paper, and computes new atomic positions (if relaxat=1) and
lattice constant (if relaxstr=1).
Then, the user uses these parameters to perform a new ground-state
and linear-response calculation. This must be repeated until
convergence is
reached. THe user can also fix some atomic positions, or strains,
thanks to the input variables
natfix,
nstrfix,
iatfix,
istrfix.
In case both relaxat
and relaxstr are 0, while
polflag=1, ANADDB only computes the polarization in cartesian
coordinates.
As described in the Na Sai's paper, it is important
to use the
finite difference expression of the ddk (berryopt=2 or -2)
in the linear response calculation of the effective charges and the
piezoelectric tensor.
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| List of ANADDB input
variables
prtdos
Mnemonics: PRinT the phonon Density Of States
Characteristic:
Variable type: integer
Default : 0
The prtdos variable is used to calculate
the phonon density of states, PHDOS, by Fourier interpolating the interatomic force
constants on the (dense) q-mesh defined by ng2qpt.
Note that the variable ifcflag must be set to 1
since the interatomic force constants are supposed to be known.
The available options are:
- 0 => no output of PHDOS (default);
- 1 => calculate PHDOS using the gaussian method and the broadening defined
by dossmear.
The step of the frequency grid employed to calculate the DOS
can be defined through the input variable dosdeltae.
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| List of ANADDB input
variables
prtfsurf
Mnemonics: PRinT the Fermi SURFace
Characteristic:
Variable type: integer
Default: 0
Only for electron-phonon calculations. The available
options are:
- 0 => do not write the Fermi Surface;
- 1 => write out the Fermi Surface in the BXSF format used by XCrySDen.
Further comments :
a) Only the eigenvalues for k-points inside the
Irreducible Brillouin zone are required. As a consequence it is
possible to use kptopt
=1 during the GS calculation to reduce
the computational effort.
b) Only unshifted k-grids that are orthogonal in
reduced space are supported by XCrySDen.
This implies that shiftk
must be set to (0,0,0) during the GS calculation
with nshiftk=1.
Furthermore if kptrlatt
is used to generate the k-grid, all the off-diagonal elements of this
array must be zero.
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variables
prtmbm
Mnemonics: PRinT Mode-By-Mode decomposition of
the electrooptic tensor
Characteristic:
Variable type: integer
Default: 0
- 0 => do not write the mode-by-mode decomposition of the
electrooptic tensor;
- 1 => write out the contribution of the individual zone-center
phonon modes to the electrooptic tensor.
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variables
prtnest
Mnemonics: PRinT the NESTing function
Characteristic:
Variable type: integer
Default: 0
In case polflag=1, ANADDB solves the linear system of equations (13)
of the Na Sai paper, and computes new atomic positions
(if relaxat=1) and
lattice constant (if relaxstr=1).
Then, the user uses these parameters to perform a new ground-state
and linear-response calculation. This must be repeated until convergence is
reached. THe user can also fix some atomic positions, or strains,
thanks to the input variables
natfix,
nstrfix,
iatfix,
istrfix.
In case both relaxat
and relaxstr are 0, while
polflag=1, ANADDB only computes the polarization in cartesian
coordinates.
As described in the Na Sai's paper, it is important to use the
finite difference expression of the ddk (berryopt=2 or -2)
in the linear response calculation of the effective charges and the piezoelectric tensor.
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prtfsurf
Mnemonics: PRinT the Fermi SURFace
Characteristic:
Variable type: integer
Default: 0
Only for electron-phonon calculations. The available options are:
- 0 => do not write the Fermi Surface;
- 1 => write out the Fermi Surface in the BXSF format used by
XCrySDen.
Further comments :
a) Only the eigenvalues for k-points inside the Irreducible
Brillouin zone are required. As a consequence it is possible to use
kptopt =1 during the GS calculation to reduce
the computational effort.
b) Only unshifted k-grids that are orthogonal in reduced space are supported by
XCrySDen. This implies that
shiftk must be set to (0,0,0) during the GS calculation
with nshiftk=1.
Furthermore if kptrlatt is used to generate the k-grid, all the off-diagonal elements of this array must be zero.
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prtmbm
Mnemonics: PRinT Mode-By-Mode decomposition
of the electrooptic tensor
Characteristic:
Variable type: integer
Default: 0
- 0 => do not write the mode-by-mode decomposition of the electrooptic tensor;
- 1 => write out the contribution of the individual zone-center phonon modes
to the electrooptic tensor.
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prtnest
Mnemonics: PRinT the NESTing function
Characteristic:
Variable type: integer
Default: 0
Only for electron-phonon calculations.
This input variable is used to calculate the nesting function defined as:
\chi_{nm}(q) = \sum_k \delta(\epsilon_{k,n}-epsilon_F) \delta(\epsilon_{k+q,m}-\epsilon_F).
The nesting factor is calculated for every point of the k-grid
employed during the previous GS calculation.
The values are subsequently interpolated along the trajectory in q space
defined by qpath, and written in the _NEST
file using the X-Y format (prtnest=1).
It is also possible to analyze the behavior of the function
in the reciprocal unit cell saving the values in the NEST_XSF file that can be read
using XCrySDen (prtnest=2).
Note that in the present implementation what is really printed to file is
the "total nesting" defined as \sum_{nm} \chi_{nm}(q).
Limitations: the k-grid defined by
kptrlatt
must be orthogonal in reciprocal space,
moreover off-diagonal elements are not allowed, i.e
kptrlatt 4 0 0 0 4 0 0 0 4 is fine while
kprtlatt = 1 0 0 0 1 1 0 -1 1 will not work.
0 => do not write the nesting function;
1 => write only the nesting function along the q-path in the X-Y format;
2 => write out the nesting function both in the X-Y and in the XSF format.
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qpath
Mnemonics: Q wavevectors defining a PATH
Characteristic:
Variable type: real array qpath(3,nqpath)
Default: qpath(:,:)=0.0
It is used to generate the path along which the phonon band structure and
phonon linewidths are interpolated.
There are nqpath-1 segments to be
defined, each of which starts from the end point of the previous one.
The number of divisions in each segment is automatically calculated
inside the code to respect the proportion between the segments.
The same circuit is used for the output of the nesting function if
prtnest=1.
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qph1l
Mnemonics: Q for PHonon List 1
Characteristic:
Variable type:
real array qph1l(4,nph1l)
Default: 0
List of nph1l
wavevectors,
defined by 4 numbers :
the wavevector is made by the three first numbers
divided by the fourth one (a normalisation factor).
The coordinates are defined with respect to the unit vectors
that spans the Brillouin zone. Note that this set of axes
can be non-orthogonal and not normed.
The normalisation factor makes easier the input of wavevector
such as (1/3,1/3,1/3), represented by 1.0 1.0 1.0 3.0 .
The internal representation of this array is as follows :
for each wavevector, the three first numbers are stored
in the array qph1l(3,nph1l), while the fourth is stored
in the array qnrml1(nph1l).
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qph2l
Mnemonics: PHonon List 2
Characteristic:
Variable type:
real array qph2l(4,nph2l)
Default: all 0
Still four numbers, but the last one, that correspond to
the normalisation factor, is 0.0
For the code, this has the meaning that the three previous
value define a direction. The direction is in CARTESIAN
COORDINATES, unlike the non-Gamma wavevectors defined in the
first list of vectors...
Note that if the three first numbers are zero, then
the code will do a calculation at Gamma without
non-analyticities.
Also note that the code automatically set the imaginary
part of the dynamical matrix to zero. This is useful to compute
the phonon frequencies when half of the k-points has been
used, by the virtue of the time-reversal symmetry (which
may induce parasitic imaginary parts...).
The internal representation of this array is as follows :
for each wavevector, the three first numbers are stored
in the array qph2l(3,nph2l), while the fourth is stored
in the array qnrml2(nph2l).
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variables
q1shft
Mnemonics: Q shifts for the grid number 1
Characteristic:
Variable type:
real array q1shft(3,nqshft)
Default: all 0.0
This vector gives the shifts needed to define the
coarse q-point grid.
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q1shft
Mnemonics: Q shifts for the grid number 1
Characteristic:
Variable type:
real array q1shft(3,nqshft)
Default: all 0.0
This vector gives the shifts needed to define the coarse q-point grid.
a) Case nqshft=1
In general, 0.5 0.5 0.5 with the ngqpt's even will give
very economical grids. On the other hand, is it
sometimes better for phonons to have the Gamma point
in the grid. In that case, 0.0 0.0 0.0 should be OK.
For the hexagonal lattice, the above mentioned
quantities become 0.0 0.0 0.5 and 0.0 0.0 0.0 .
b) Case nqshft=2
The two q1shft vectors must form a BCC lattice.
For example, use 0.0 0.0 0.0 and 0.5 0.5 0.5
c) Case nqshft=4
The four q1shft vectors must form a FCC lattice.
For example, use 0.0 0.0 0.0 , 0.0 0.5 0.5 ,
0.5 0.0 0.5 , 0.5 0.5 0.0
or 0.5 0.5 0.5 , 0.0 0.0 0.5 ,
0.0 0.5 0.0 , 0.5 0.0 0.0 (the latter is referred to
as shifted)
Further comments : by using this technique, it is possible
to increase smoothly the number of q-points, at least
less abruptly than relying on series of grids like
(for the full cubic symmetry)
1x1x1 => (0 0 0)
2x2x2 (shifted) => (.25 .25 .25)
2x2x2 => 1x1x1 + (.5 0 0) (.5 .5 0) (.5 .5 0)
4x4x4 => 2x2x2 + (.25 0 0) (.25 .25 0) (.25 .5 0)
(.25 .25 .25) (.25 .25 .5) (.25 .5 .5)
...
with respectively 1, 1, 4 and 10 q-points, corresponding
to a number of points in the full BZ of 1, 8, 8 and 64.
Indeed, the following grids are made available :
1x1x1 with nqshft=2 => (0 0 0) (.5 .5 .5)
1x1x1 with nqshft=4 => (0 0 0) (.5 .5 0)
1x1x1 with nqshft=4 (shifted) => (.5 0 0) (.5 .5 .5)
2x2x2 with nqshft=2 => 2x2x2 + (.25 .25 .25)
2x2x2 with nqshft=4 => 2x2x2 + (.25 .25 0) (.25 .25 .5)
2x2x2 with nqshft=4 (shifted) => (.25 0 0) (.25 .25 .25)
(.5 .5 .25) (.25 .5 0)
...
with respectively 2, 2, 2, 5, 6 and 4 q-points, corresponding
to a number of points in the full BZ of 2, 4, 4, 16, 32 and 32.
For a FCC lattice, it is possible to sample only the Gamma point
by using a 1x1x1 BCC sampling (nqshft=2).
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q2shft
Mnemonics: Q points SHiFTs for the grids 2
Characteristic:
Variable type: real array q2shft(3)
Default: all 0
Similar to q1shft,
but for the series of fine grids.
Note that nqshft
for this series of grids corresponds to 1.
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ramansr
Mnemonics: RAMAN Sum-Rule
Characteristic:
Variable type: integer
Default: 0
Govern the imposition of the sum-rule on the Raman tensors.
As in the case of the Born effective charges, the first-order derivatives
of the linear dielectric susceptibility with respect to an atomic displacement
must vanish when they are summed over all atoms. This sum rule is broken
in most calculations. By putting ramansr equal to 1 or 2, this sum
rule is imposed by giving each atom a part of the discrepancy.
- 0 => no sum rule is imposed;
- 1 => impose the sum rule on the Raman tensors, giving each
atom an equal part of the discrepancy;
- 2 => impose the sum rule on the Raman tensors, giving each
atom a part of the discrepancy proportional to the magnitude of its
contribution to the Raman tensor.
For the time being, ramansr=1 is the preferred choice.
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variables
relaxat
Mnemonics: RELAXation of AToms
Characteristic:
Variable type: integer
Default: 0
If relaxat=1, relax atomic positions during a
structural relaxation
at constrained polarization.
See polflag.
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variables
relaxstr
Mnemonics: RELAXation of STRain
Characteristic:
Variable type: integer
Default: 0
If relaxat=1, relax lattice constants
(lengths/angles) during a structural relaxation
at constrained polarization. See polflag.
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relaxstr
Mnemonics: RELAXation of STRain
Characteristic:
Variable type: integer
Default: 0
If relaxat=1, relax lattice constants (lengths/angles) during a structural relaxation
at constrained polarization.
See polflag.
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rfmeth
Mnemonics: Response-Function METHod
Characteristic:
Variable type: integer
Default: 1
Select a particular set of Data Blocks in the DDB.
(PRESENTLY, ONLY OPTION 1 IS AVAILABLE)
- 1 => Blocks obtained by a non-stationary formulation.
- 2 => Blocks obtained by a stationary formulation.
For more detailed explanations, see abinis_help
If the information in the DDB is available, always use
the option 2. If not, you can try option 1, which is less
accurate.
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rifcsph
Mnemonics: Radius of the Interatomic Force Constant SPHere
Characteristic:
Variable type: real
Default: zero
Cut-off radius for the sphere for
interatomic force constant, see also the alternative nsphere.
If rifcsph= 0 : maximum extent allowed by the grid .
This number defines the atoms for which the
short range part of the interatomic force constants, after
imposition of the acoustic sum rule, will not be put to zero.
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variables
selectz
Mnemonics: SeLECT Z
Characteristic:
Variable type: integer
Default: 0
Select some parts of the effective charge tensor.
(This is done after the application or non-application of the ASR for
effective charges). The transformed effective charges are then used for
all the subsequent calculations.
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selectz
Mnemonics: SeLECT Z
Characteristic:
Variable type: integer
Default: 0
Select some parts of the effective charge tensor.
(This is done after the application or non-application of
the ASR for effective charges). The transformed effective
charges are then used for all the subsequent calculations.
- 0 => The effective charge tensor is left as it is.
- 1 => For each atom, the effective charge tensor is made
isotropic, by calculating the trace of the matrix,
dividing it by 3, and using this number in a
diagonal effective charge tensor.
- 2 => For each atom, the effective charge tensor is made
symmetric, by simply averaging on symmetrical elements.
-
Note : this is for analysis the effect of anisotropy
in the effective charge. The result with non-zero selectz
are unphysical.
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variables
symdynmat
Mnemonics: SYMmetrize the DYNamical MATrix
Characteristic:
Variable type: integer
Default: 1 (was 0 before v5.3)
If symdynmat is equal to 1, the dynamical
matrix
is symmetrized before the diagonalization.
This is especially useful when the set of primitive vectors of the unit
cell
and their opposite do not reflect the symmetries of the Bravais lattice
(typical case : body-centered tetragonal lattices ; FCC and BCC lattices
might be treated with the proper setting of the
brav
variable),
and the interpolation
procedure based on interatomic force constant is used : there are some
slight symmetry breaking effects. The latter can be bypassed by this
additional
symmetrization.
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variables
targetpol
Mnemonics: TARGET POLarization
Characteristic:
Variable type: real targetpol(1:3)
Default: 0.0
Target value of the polarization in cartesian
coordinates and in C/m^2.
See polflag.
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variables
telphint
Mnemonics: Technique for ELectron-PHonon
INTegration
Characteristic:
Variable type: integer
Default: 1
Flag controlling the Fermi surface integration
technique used for electron-phonon quantities.
- 0 = tetrahedron method (no adjustable parameter)
- 1 = Gaussian smearing (see elphsmear)
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telphint
Mnemonics: Technique for ELectron-PHonon INTegration
Characteristic:
Variable type: integer
Default: 1
Flag controlling the Fermi surface integration technique used
for electron-phonon quantities.
- 0 = tetrahedron method (no adjustable parameter)
- 1 = Gaussian smearing (see elphsmear)
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temperinc
Mnemonics: TEMPERature INCrease
Characteristic:
Variable type: real
Default: 2.0
Increment of the temperature in Kelvin, for thermodynamical properties.
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tempermin
Mnemonics: TEMPERature MINimum
Characteristic:
Variable type: real
Default: 1.0
Lowest temperature (Kelvin) at which the thermodynamical quantities
have to be evaluated. Cannot be zero.
The highest temperature is defined using
temperinc
and ntemper.
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thmflag
Mnemonics: THerMal FLAG
Characteristic:
Variable type: integer
Default: 0
When non-zero, the code will compute, using the histogram method :
- the normalized phonon DOS
- the phonon internal energy, free energy,
entropy, constant volume heat capacity
as a function of the temperature
- the Debye-Waller factors (tensors) for
each atom, as a function of the temperature
- the "average frequency"
as a function of the temperature
(if iavfrq=1)
When thmflag is equal to 2, all the phonon frequencies for the
q points in the second grid are printed.
Input variables needed if this flag is activated :
dostol,
nchan,
ntemper,
temperinc,
tempermin,
as well as the wavevector grid number 2 definition,
ng2qpt,
ngrids,
q2shft.
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thmtol
Mnemonics: THerModynamic TOLerance
Characteristic:
Variable type: real
Default: 0.05
The relative tolerance on the thermodynamical functions
This number will determine when the series of channel widths
with which the DOS is calculated can be stopped, i.e.
the mean of the relative change going from one grid
to the next bigger is smaller than thmtol.
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variables
vrsinddb
Mnemonics: VeRSion of the DDB
Characteristic:
Variable type: integer
Default: 990527
6 digit integer, giving the version of the
DDB that will be input to the Anaddb code. Should be equal
to the DDB version supported by the code.
The format is yymmdd, where dd is the day number,
mm is the month number and yy is the
two last digits of the year number.
The default is fine in all present cases.
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variables
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Help files :
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