# Input File Description ## Program: ph.x / PWscf / Quantum Espresso (version: 6.7)
> > ### TABLE OF CONTENTS INTRODUCTION Line-of-input: title_line &INPUTPH amass | outdir | prefix | niter_ph | tr2_ph | alpha_mix(niter) | nmix_ph | verbosity | reduce_io | max_seconds | fildyn | fildrho | fildvscf | epsil | lrpa | lnoloc | trans | lraman | eth_rps | eth_ns | dek | recover | low_directory_check | only_init | qplot | q2d | q_in_band_form | electron_phonon | el_ph_nsigma | el_ph_sigma | ahc_dir | ahc_nbnd | ahc_nbndskip | skip_upperfan | lshift_q | zeu | zue | elop | fpol | ldisp | nogg | asr | ldiag | lqdir | search_sym | nq1 | nq2 | nq3 | nk1 | nk2 | nk3 | k1 | k2 | k3 | diagonalization | read_dns_bare | ldvscf_interpolate | wpot_dir | do_long_range | do_charge_neutral | start_irr | last_irr | nat_todo | modenum | start_q | last_q | dvscf_star | drho_star Line-of-input: xq(1) xq(2) xq(3) qPointsSpecs nqs | xq1 | xq2 | xq3 | nq Line-of-input: atom(1) atom(2) ... atom(nat_todo) ADDITIONAL INFORMATION ### INTRODUCTION
> >     Input data format: { } = optional, [ ] = it depends, # = comment

> >     Structure of the input data:
> >     ===============================================================================

> >     title_line

> >     &INPUTPH
> >        ...
> >     /

> >     [ xq(1) xq(2) xq(3) ]                        # if ldisp != .true.  and  qplot != .true.

> >     [ nqs                                        # if qplot == .true.
> >       xq(1,i)    xq(2,i)    xq(3,1)    nq(1)
> >       ...
> >       xq(1,nqs)  xq(2,nqs)  xq(3,nqs)  nq(nqs) ]

> >     [ atom(1)  atom(2)  ... atom(nat_todo) ]     # if nat_todo was specified
### Line of input
### Syntax: title_line
> ### Description of items:
> title_line | CHARACTER
> >     Title of the job, i.e., a line that is reprinted on output.
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## Namelist: &INPUTPH
amass(i), i=1,ntyp | REAL
Default: | 0.0
>     Atomic mass [amu] of each atomic type.
>     If not specified, masses are read from data file.
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outdir | CHARACTER
Default: | value of the `ESPRESSO_TMPDIR` environment variable if set; current directory ('./') otherwise
>     Directory containing input, output, and scratch files;
>     must be the same as specified in the calculation of
>     the unperturbed system.
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prefix | CHARACTER
Default: | 'pwscf'
>     Prepended to input/output filenames; must be the same
>     used in the calculation of unperturbed system.
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niter_ph | INTEGER
Default: | maxter=100
>     Maximum number of iterations in a scf step. If you want
>     more than 100, edit variable "maxter" in PH/phcom.f90
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tr2_ph | REAL
Default: | 1e-12
>      Threshold for self-consistency.
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alpha_mix(niter) | REAL
Default: | alpha_mix(1)=0.7
>     Mixing factor (for each iteration) for updating
>     the scf potential:

>     vnew(in) = alpha_mix*vold(out) + (1-alpha_mix)*vold(in)
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nmix_ph | INTEGER
Default: | 4
>      Number of iterations used in potential mixing.
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verbosity | CHARACTER
Default: | 'default'
>      Options are:
>   `'debug', 'high', 'medium' :`
>        verbose output
>   `'low', 'default', 'minimal' :`
>        short output
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reduce_io | LOGICAL
Default: | .false.
>      Reduce I/O to the strict minimum.
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max_seconds | REAL
Default: | 1.d7
>      Maximum allowed run time before the job stops smoothly.
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fildyn | CHARACTER
Default: | 'matdyn'
>      File where the dynamical matrix is written.
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fildrho | CHARACTER
Default: | ' '
>     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
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fildvscf | CHARACTER
Default: | ' '
>     File where the the potential variation is written
>     (for later use in electron-phonon calculation, see also fildrho).
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epsil | LOGICAL
Default: | .false.
>     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).
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lrpa | LOGICAL
Default: | .false.
>     If .true. the dielectric constant is calculated at the
>     RPA level with DV_xc=0.
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lnoloc | LOGICAL
Default: | .false.
>     If .true. the dielectric constant is calculated without
>     local fields, i.e. by setting DV_H=0 and DV_xc=0.
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trans | LOGICAL
Default: | .true.
>     If .true. the phonons are computed.
>     If trans .and. epsil are .true. effective charges are
>     calculated.
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lraman | LOGICAL
Default: | .false.
>     If .true. calculate non-resonant Raman coefficients
>     using second-order response as in:
>     M. Lazzeri and F. Mauri, PRL 90, 036401 (2003).
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Optional variables for Raman:
eth_rps | REAL
Default: | 1.0d-9
>      Threshold for calculation of  Pc R |psi>.
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eth_ns | REAL
Default: | 1.0e-12
>      Threshold for non-scf wavefunction calculation.
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dek | REAL
Default: | 1.0e-3
>      Delta_xk used for wavefunction derivation wrt k.
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recover | LOGICAL
Default: | .false.
>      If .true. restart from an interrupted run.
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low_directory_check | LOGICAL
Default: | .false.
>     If .true. search in the phsave directory only the
>                      quantities requested in input.
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only_init | LOGICAL
Default: | .false.
>     If .true. only the bands and other initialization quantities are calculated.
>     (used for GRID parallelization)
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qplot | LOGICAL
Default: | .false.
>      If .true. a list of q points is read from input.
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q2d | LOGICAL
Default: | .false.
>     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.
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q_in_band_form | LOGICAL
Default: | .false.
>     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.
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electron_phonon | CHARACTER
Default: | ' '
>     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.
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el_ph_nsigma | INTEGER
Default: | 10
>     The number of double-delta smearing values used in an
>     electron-phonon coupling calculation.
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el_ph_sigma | REAL
Default: | 0.02
>     The spacing between double-delta smearing values used in
>     an electron-phonon coupling calculation.
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Variables for electron_phonon = 'ahc':
ahc_dir | CHARACTER
Default: | outdir // 'ahc_dir/'
>     Directory where the output binary files are written.
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ahc_nbnd | INTEGER
Status: | REQUIRED
>     Number of bands for which the electron self-energy is to be computed.
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ahc_nbndskip | INTEGER
Default: | 0
>     Number of bands to exclude when computing the self-energy. Self-energy
>     is computed for bands with indices from ahc_nbndskip+1 to
>     ahc_nbndskip+ahc_nbnd. ahc_nbndskip+ahc_nbnd cannot
>     exceed nbnd of the preceding SCF or NSCF calculation.
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skip_upperfan | LOGICAL
Default: | .false.
>     If .true., skip calculation of the upper Fan self-energy, which
>     involves solving the Sternheimer equation.
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lshift_q | LOGICAL
Default: | .false.
>     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.
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zeu | LOGICAL
Default: | zeu=epsil
>     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.
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zue | LOGICAL
Default: | .false.
>     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.
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elop | LOGICAL
Default: | .false.
>     If .true. calculate electro-optic tensor.
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fpol | LOGICAL
Default: | .false.
>     If .true. calculate dynamic polarizabilities
>     Requires epsil=.true. ( experimental stage:
>     see example09 for calculation of methane ).
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ldisp | LOGICAL
Default: | .false.
>     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.
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nogg | LOGICAL
Default: | .false.
>     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.
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asr | LOGICAL
Default: | .false.
>     Apply Acoustic Sum Rule to dynamical matrix, effective charges
>     Works only in conjunction with "gamma_gamma" tricks (see above)
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ldiag | LOGICAL
Default: | .false.
>     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.
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lqdir | LOGICAL
Default: | .false.
>     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.
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search_sym | LOGICAL
Default: | .true.
>     Set it to .false. if you want to disable the mode
>     symmetry analysis.
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nq1, nq2, nq3 | INTEGER
Default: | 0,0,0
>     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.
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nk1, nk2, nk3, k1, k2, k3 | INTEGER
Default: | 0,0,0,0,0,0
>     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.
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diagonalization | CHARACTER
Default: | 'david'
>     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.
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read_dns_bare | LOGICAL
Default: | .false.
>     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.
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ldvscf_interpolate | LOGICAL
Default: | .false.
>     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..
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Optional variables for dvscf interpolation:
wpot_dir | CHARACTER
Default: | outdir // 'w_pot/'
>     Directory where the w_pot binary files are written.
>     Must be the same with wpot_dir used in dvscf_q2r.x.
>     The real space potential files are stored in wpot_dir
>     with names ${prefix}.wpot.irc${irc}//"1".
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do_long_range | LOGICAL
Default: | .false.
>     If .true., add the long-range part of the potential
>     to the Fourier interpolated potential as in:
>     S. Ponce et al, J. Chem. Phys. 143, 102813 (2015).
>     Reads dielectric matrix and Born effective charges from
>     the ${wpot_dir}/tensors.dat file, written in dvscf_q2r.x.
>     Currently, only the dipole (Frohlich) part is implemented.
>     The quadrupole part is not implemented.
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do_charge_neutral | LOGICAL
Default: | .false.
>     If .true., impose charge neutrality on the Born effective
>     charges. Used only if do_long_range = .true..
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Specification of irreducible representation
start_irr | INTEGER
Default: | 1
See: | last_irr
>     Perform calculations only from start_irr to last_irr
>     irreducible representations.

>     IMPORTANT:
>        * start_irr must be <= 3*nat
>        * do not specify nat_todo together with
>          start_irr, last_irr
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last_irr | INTEGER
Default: | 3*nat
See: | start_irr
>     Perform calculations only from start_irr to last_irr
>     irreducible representations.

>     IMPORTANT:
>        * start_irr must be <= 3*nat
>        * do not specify nat_todo together with
>          start_irr, last_irr
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nat_todo | INTEGER
Default: | 0, i.e. displace all atoms
>     Choose the subset of atoms to be used in the linear response
>     calculation: nat_todo atoms, specified in input (see below)
>     are displaced. Can be used to estimate modes for a molecule
>     adsorbed over a surface without performing a full fledged
>     calculation. Use with care, at your own risk, and be aware
>     that this is an approximation and may not work.
>     IMPORTANT:
>        * nat_todo <= nat
>        * if linear-response is calculated for a given atom, it
>          should also be done for all symmetry-equivalent atoms,
>          or else you will get incorrect results
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modenum | INTEGER
Default: | 0
>     For single-mode phonon calculation : modenum is the index of the
>     irreducible representation (irrep) into which the reducible
>     representation formed by the 3*nat atomic displacements are
>     decomposed in order to perform the phonon calculation.
>     Note that a single-mode calculation will not give you the
>     frequency of a single phonon mode: in general, the selected
>     "modenum" is not an eigenvector. What you get on output is
>     a column of the dynamical matrix.
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q-point specification
start_q | INTEGER
Default: | 1
See: | last_q
>     Used only when ldisp=.true..
>     Computes only the q points from start_q to last_q.

>     IMPORTANT:
>        * start_q must be <= nqs (number of q points found)
>        * do not specify nat_todo together with
>          start_q, last_q
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last_q | INTEGER
Default: | number of q points
See: | start_q
>     Used only when ldisp=.true..
>     Computes only the q points from start_q to last_q.

>     IMPORTANT
>        * last_q must be <= nqs (number of q points)
>        * do not specify nat_todo together with
>          start_q, last_q
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dvscf_star | STRUCTURE
Default: | disabled
>     It contains the following components:

>     dvscf_star%open  (logical, default: .false.)
>     dvscf_star%dir   (character, default: outdir//"Rotated_DVSCF" or the
>                       ESPRESSO_FILDVSCF_DIR environment variable)
>     dvscf_star%ext   (character, default: "dvscf") the extension to use
>                       for the name of the output files, see below
>     dvscf_star%basis (character, default: "cartesian") the basis on which
>                       the rotated dvscf will be saved
>     dvscf_star%pat   (logical, default: false) save an optional file with the
>                       displacement patterns and q vector for each dvscf file

>     IF dvscf_star%open is .true. use symmetry to compute and store the variation
>     of the self-consistent potential on every q* in the star of the present q.

>     The rotated dvscf will then be stored in directory dvscf_star%dir with name
>     prefix.dvscf_star%ext.q_name//"1". Where q_name is derived from the coordinates
>     of the q-point, expressed as fractions in crystalline coordinates
>     (notice that ph.x reads q-points in cartesian coordinates).
>     E.g. q_cryst= (0, 0.5, -0.25) -> q_name = "0_1o2_-1o4"

>     The dvscf can be represented on a basis of cartesian 1-atom displacements
>     (dvscf_star%basis='cartesian') or on the basis of the modes at the rotated q-point
>     (dvscf_star%basis='modes'). Notice that the el-ph wannier code requires 'cartesian'.
>     Each dvscf file comes with a corresponding pattern file with an additional ".pat"
>     suffix; this file contains information about the basis and the q-point of the dvscf.

>     Note: rotating dvscf can require a large amount of RAM memory and can be i/o
>           intensive; in its current implementation all the operations are done
>           on a single processor.
>     Note2: this feature is currently untested with image parallelisation.
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drho_star | STRUCTURE
Default: | disabled
See: | dvscf_star
>     It contains the following components:

>     drho_star%open  (logical, default: .false.)
>     drho_star%dir   (character, default: outdir//"Rotated_DRHO" or the
>                      ESPRESSO_FILDRHO_DIR environment variable)
>     drho_star%ext   (character, default: "drho") the extension to use
>                      for the name of the output files, see below
>     drho_star%basis (character, default: "modes") the basis on which
>                      the rotated drho will be saved
>     drho_star%pat   (logical, default: true) save an optional file with the
>                      displacement patterns and q vector for each drho file

>     Like dvscf_star, but for the perturbation of the charge density.
>     Notice that the defaults are different.
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> IF `ldisp != .true. and qplot != .true. :`
> ### Line of input
> ### Syntax: xq(1) xq(2) xq(3)
> > ### Description of items:
> > xq(1) xq(2) xq(3) | REAL
> > >     The phonon wavevector, in units of 2pi/a0
> > >     (a0 = lattice parameter).
> > >     Not used if ldisp=.true. or qplot=.true.
> [Back to Top]
> ELSEIF `qplot == .true. :`
> Specification of q points when qplot == .true.
> ## Card: qPointsSpecs
> > ### Syntax: nqs
> > xq1(1) | xq2(1) | xq3(1) | nq(1)
> > xq1(2) | xq2(2) | xq3(2) | nq(2)
> > . . .
> > xq1(nqs) | xq2(nqs) | xq3(nqs) | nq(nqs)
> > ### Description of items:
> > nqs | INTEGER
> > >     Number of q points in the list. Used only if qplot=.true.
> > [Back to Top]
> > xq1, xq2, xq3 | REAL
> > >     q-point coordinates; used only with ldisp=.true. and qplot=.true.
> > >     The phonon wavevector, in units of 2pi/a0 (a0 = lattice parameter).
> > >     The meaning of these q points and their weights nq depend on the
> > >     flags q2d and q_in_band_form. (NB: nq is integer)
> > [Back to Top]
> > nq | INTEGER
> > >     The weight of the q-point; the meaning of nq depends
> > >     on the flags q2d and q_in_band_form.
> [Back to Top]
> IF `nat_todo was specified :`
> ### Line of input
> ### Syntax: atom(1) atom(2) ... atom(nat_todo)
> > ### Description of items:
> > atom(1) atom(2) ... atom(nat_todo) | INTEGER
> > >     Contains the list of indices of atoms used in the
> > >     calculation if nat_todo is specified.
> [Back to Top]
> > ### ADDITIONAL INFORMATION
> >     NB: The program ph.x writes on the tmp_dir/_ph0/{prefix}.phsave directory
> >     a file for each representation of each q point. This file is called
> >     dynmat.#iq.#irr.xml where #iq is the number of the q point and #irr
> >     is the number of the representation. These files contain the
> >     contribution to the dynamical matrix of the irr representation for the
> >     iq point.

> >     If recover=.true. ph.x does not recalculate the
> >     representations already saved in the tmp_dir/_ph0/{prefix}.phsave
> >     directory.  Moreover ph.x writes on the files patterns.#iq.xml in the
> >     tmp_dir/_ph0/{prefix}.phsave directory the displacement patterns that it
> >     is using. If recover=.true. ph.x does not recalculate the
> >     displacement patterns found in the tmp_dir/_ph0/{prefix}.phsave directory.

> >     This mechanism allows:

> >       1) To recover part of the ph.x calculation even if the recover file
> >          or files are corrupted. You just remove the _ph0/{prefix}.recover
> >          files from the tmp_dir directory. You can also remove all the _ph0
> >          files and keep only the _ph0/{prefix}.phsave directory.

> >       2) To split a phonon calculation into several jobs for different
> >          machines (or set of nodes). Each machine calculates a subset of
> >          the representations and saves its dynmat.#iq.#irr.xml files on
> >          its tmp_dir/_ph0/{prefix}.phsave directory. Then you collect all the
> >          dynmat.#iq.#irr.xml files in one directory and run ph.x to
> >          collect all the dynamical matrices and diagonalize them.

> >     NB: To split the q points in different machines, use the input
> >     variables start_q and last_q. To split the irreducible
> >     representations, use the input variables start_irr, last_irr. Please
> >     note that different machines will use, in general, different
> >     displacement patterns and it is not possible to recollect partial
> >     dynamical matrices generated with different displacement patterns.  A
> >     calculation split into different machines will run as follows: A
> >     preparatory run of ph.x with start_irr=0, last_irr=0 produces the sets
> >     of displacement patterns and save them on the patterns.#iq.xml files.
> >     These files are copied in all the tmp_dir/_ph0/{prefix}.phsave directories
> >     of the machines where you plan to run ph.x. ph.x is run in different
> >     machines with complementary sets of start_q, last_q, start_irr and
> >     last_irr variables.  All the files dynmat.#iq.#irr.xml are
> >     collected on a single tmp_dir/_ph0/{prefix}.phsave directory (remember to
> >     collect also dynmat.#iq.0.xml).  A final run of ph.x in this
> >     machine collects all the data contained in the files and diagonalizes
> >     the dynamical matrices.  This is done requesting a complete dispersion
> >     calculation without using start_q, last_q, start_irr, or last_irr.
> >     See an example in examples/GRID_example.

> >     On parallel machines the q point and the irreps calculations can be split
> >     automatically using the -nimage flag. See the phonon user guide for further
> >     information.

This file has been created by helpdoc utility on Sun Nov 29 12:16:13 CET 2020.