Input File Description

Atomic mass [amu] of each atomic type.
If not specified, masses are read from data file.
         

Directory containing input, output, and scratch files;
must be the same as specified in the calculation of
the unperturbed system.
         

Prepended to input/output filenames; must be the same
used in the calculation of unperturbed system.
         

Maximum number of iterations in a scf step. If you want
more than 100, edit variable "maxter" in PH/phcom.f90
         

 Threshold for self-consistency.
         

Mixing factor (for each iteration) for updating
the scf potential:

vnew(in) = alpha_mix*vold(out) + (1-alpha_mix)*vold(in)
         

Number of iterations used in potential mixing. Using a larger value (8~20)
can significantly speed up convergence, at the cost of using more memory.
         

 Options are:
            

'debug', 'high', 'medium' :

 verbose output
            

'low', 'default', 'minimal' :

 short output
            

Reduce I/O to the strict minimum.

BEWARE: If the input flag reduce_io=.true. was
used, it is not allowed to restart from an interrupted
run.
         

 Maximum allowed run time before the job stops smoothly.
         

 File where the dynamical matrix is written.
         

File where the charge density responses are written. Note that the file
will actually be saved as ${outdir}/_ph0/${prefix}.${fildrho}1
where  ${outdir}, ${prefix} and ${fildrho} are the values of the
corresponding input variables
         

File where the the potential variation is written
(for later use in electron-phonon calculation, see also fildrho).
         

If .true. in a q=0 calculation for a non metal the
macroscopic dielectric constant of the system is
computed. Do not set epsil to .true. if you have a
metallic system or q/=0: the code will complain and stop.

Note: the input value of epsil will be ignored if ldisp=.true.
(the code will automatically set epsil to .false. for metals,
to .true. for insulators: see routine PHonon/PH/prepare_q.f90).
         

If .true. the dielectric constant is calculated at the
RPA level with DV_xc=0.
         

If .true. the dielectric constant is calculated without
local fields, i.e. by setting DV_H=0 and DV_xc=0.
         

If .false. the phonons are not computed.
If trans .and. epsil are both .true.,
the effective charges are calculated.
If ldisp is .true., trans=.false. is overridden
(except for the case of electron-phonon calculations)
         

If .true. calculate non-resonant Raman coefficients
using second-order response as in:
M. Lazzeri and F. Mauri, PRL 90, 036401 (2003).
         

Optional variables for Raman:

 If .true. restart from an interrupted run.
         

If .true. search in the phsave directory only the
                 quantities requested in input.
         

If .true. only the bands and other initialization quantities are calculated.
(used for GRID parallelization)
         

 If .true. a list of q points is read from input.
         

If .true. three q points and relative weights are
read from input. The three q points define the rectangle
q(:,1) + l (q(:,2)-q(:,1)) + m (q(:,3)-q(:,1)) where
0< l,m < 1. The weights are integer and those of points two
and three are the number of points in the two directions.
         

This flag is used only when qplot is .true. and q2d is
.false.. When .true. each couple of q points q(:,i+1) and
q(:,i) define the line from q(:,i) to q(:,i+1) and nq
points are generated along that line. nq is the weigth of
q(:,i). When .false. only the list of q points given as
input is calculated. The weights are not used.
         

Options are:
            

'simple' :

Electron-phonon lambda coefficients are computed
for a given q and a grid of k-points specified by
the variables nk1, nk2, nk3, k1, k2, k3.
            

'interpolated' :

Electron-phonon is calculated by interpolation
over the Brillouin Zone as in M. Wierzbowska, et
al. arXiv:cond-mat/0504077
            

'lambda_tetra' :

The electron-phonon coefficient \lambda_{q \nu}
is calculated with the optimized tetrahedron method.
            

'gamma_tetra' :

The phonon linewidth \gamma_{q \nu} is calculated
from the electron-phonon interactions
using the optimized tetrahedron method.
            

'epa' :

Electron-phonon coupling matrix elements are written
to file prefix.epa.k for further processing by program
epa.x which implements electron-phonon averaged (EPA)
approximation as described in G. Samsonidze & B. Kozinsky,
Adv. Energy Mater. 2018, 1800246 doi:10.1002/aenm.201800246
arXiv:1511.08115
            

'ahc' :

Quantities required for the calculation of phonon-induced
electron self-energy are computed and written to the directory
ahc_dir. The output files can be read by postahc.x for
the calculation of electron self-energy.
Available for both metals and insulators.
trans=.false. is required.
            

For metals only, requires gaussian smearing (except for 'ahc').

If trans=.true., the lambdas are calculated in the same
run, using the same k-point grid for phonons and lambdas.
If trans=.false., the lambdas are calculated using
previously saved DeltaVscf in fildvscf, previously saved
dynamical matrix, and the present punch file. This allows
the use of a different (larger) k-point grid.
            

The number of double-delta smearing values used in an
electron-phonon coupling calculation.
         

The spacing between double-delta smearing values used in
an electron-phonon coupling calculation.
         

Variables for electron_phonon = 'ahc':

Use a wave-vector grid displaced by half a grid step
in each direction - meaningful only when ldisp is .true.
When this option is set, the q2r.x code cannot be used.
         

If .true. in a q=0 calculation for a non metal the
effective charges are computed from the dielectric
response. This is the default algorithm. If epsil=.true.
and zeu=.false. only the dielectric tensor is calculated.
         

If .true. in a q=0 calculation for a non metal the
effective charges are computed from the phonon
density responses. This is an alternative algorithm,
different from the default one (if trans .and. epsil )
The results should be the same within numerical noise.
         

If .true. calculate electro-optic tensor.
         

If .true. calculate dynamic polarizabilities
Requires epsil=.true. ( experimental stage:
see example09 for calculation of methane ).
         

If .true. the run calculates phonons for a grid of
q-points specified by nq1, nq2, nq3 - for direct
calculation of the entire phonon dispersion.
         

If .true. disable the "gamma_gamma" trick used to speed
up calculations at q=0 (phonon wavevector) if the sum over
the Brillouin Zone includes k=0 only. The gamma_gamma
trick exploits symmetry and acoustic sum rule to reduce
the number of linear response calculations to the strict
minimum, as it is done in code phcg.x.
         

Apply Acoustic Sum Rule to dynamical matrix, effective charges
Works only in conjunction with "gamma_gamma" tricks (see above)
         

If .true. forces the diagonalization of the dynamical
matrix also when only a part of the dynamical matrix
has been calculated. It is used together with start_irr
and last_irr. If all modes corresponding to a
given irreducible representation have been calculated,
the phonon frequencies of that representation are
correct. The others are zero or wrong. Use with care.
         

If .true. ph.x creates inside outdir a separate subdirectory
for each q vector. The flag is set to .true. when ldisp=.true.
and fildvscf /= ' ' or when an electron-phonon
calculation is performed. The induced potential is saved
separately for each q inside the subdirectories.
         

Set it to .false. if you want to disable the mode
symmetry analysis.
         

Parameters of the Monkhorst-Pack grid (no offset) used
when ldisp=.true. Same meaning as for nk1, nk2, nk3
in the input of pw.x.
         

When these parameters are specified the phonon program
runs a pw non-self consistent calculation with a different
k-point grid thant that used for the charge density.
This occurs even in the Gamma case.
nk1, nk2, nk3 are the parameters of the Monkhorst-Pack grid
with offset determined by k1, k2, k3.
         

Diagonalization method for the non-SCF calculations.
            

'david' :

Davidson iterative diagonalization with overlap matrix
(default). Fast, may in some rare cases fail.
            

'cg' :

Conjugate-gradient-like band-by-band diagonalization.
Slower than 'david' but uses less memory and is
(a little bit) more robust.
            

If .true. the PH code tries to read three files in the DFPT+U
calculation: dns_orth, dns_bare, d2ns_bare.
dns_orth and dns_bare are the first-order variations of
the occupation matrix, while d2ns_bare is the second-order
variation of the occupation matrix. These matrices are
computed only once during the DFPT+U calculation. However,
their calculation (especially of d2ns_bare) is computationally
expensive, this is why they are written to file and then can be
read (e.g. for restart) in order to save time.
         

If .true., use Fourier interpolation of phonon potential
to compute the induced part of phonon potential at each
q point. Results of a dvscf_q2r.x run is needed.
Requires trans = .false..
         

Optional variables for dvscf interpolation:

Specification of irreducible representation

q-point specification