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<input_description distribution="Quantum Espresso" package="PWscf" program="ph.x" >
   <toc>
   </toc>
   <intro>
<b>Input data format:</b> { } = optional, [ ] = it depends, # = comment

<b>Structure of the input data:</b>
===============================================================================

title_line

<b>&amp;INPUTPH</b>
   ...
<b>/</b>

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

[ nqs                                        <i># if <ref>qplot</ref> == .true. </i>
  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) ]     <i># if <ref>nat_todo</ref> was specified</i>
   </intro>
   <linecard>
      <var name="title_line" type="CHARACTER" >
         <info>
Title of the job, i.e., a line that is reprinted on output.
         </info>
      </var>
   </linecard>
   <namelist name="INPUTPH" >
      <dimension name="amass" start="1" end="ntyp" type="REAL" >
         <default> 0.0
         </default>
         <info>
Atomic mass [amu] of each atomic type.
If not specified, masses are read from data file.
         </info>
      </dimension>
      <var name="outdir" type="CHARACTER" >
         <default>
value of the <tt>ESPRESSO_TMPDIR</tt> environment variable if set;
<br/> current directory (&apos;./&apos;) otherwise
         </default>
         <info>
Directory containing input, output, and scratch files;
must be the same as specified in the calculation of
the unperturbed system.
         </info>
      </var>
      <var name="prefix" type="CHARACTER" >
         <default> &apos;pwscf&apos;
         </default>
         <info>
Prepended to input/output filenames; must be the same
used in the calculation of unperturbed system.
         </info>
      </var>
      <var name="niter_ph" type="INTEGER" >
         <default> maxter=100
         </default>
         <info>
Maximum number of iterations in a scf step. If you want
more than 100, edit variable &quot;maxter&quot; in PH/phcom.f90
         </info>
      </var>
      <var name="tr2_ph" type="REAL" >
         <default> 1e-12
         </default>
         <info> Threshold for self-consistency.
         </info>
      </var>
      <var name="alpha_mix(niter)" type="REAL" >
         <default> alpha_mix(1)=0.7
         </default>
         <info>
Mixing factor (for each iteration) for updating
the scf potential:

vnew(in) = alpha_mix*vold(out) + (1-alpha_mix)*vold(in)
         </info>
      </var>
      <var name="nmix_ph" type="INTEGER" >
         <default> 4
         </default>
         <info> Number of iterations used in potential mixing.
         </info>
      </var>
      <var name="verbosity" type="CHARACTER" >
         <default> &apos;default&apos;
         </default>
         <options>
            <info> Options are:
            </info>
            <opt val="'debug', 'high', 'medium'" > verbose output
            </opt>
            <opt val="'low', 'default', 'minimal'" > short output
            </opt>
         </options>
      </var>
      <var name="reduce_io" type="LOGICAL" >
         <default> .false.
         </default>
         <info> Reduce I/O to the strict minimum.
         </info>
      </var>
      <var name="max_seconds" type="REAL" >
         <default> 1.d7
         </default>
         <info> Maximum allowed run time before the job stops smoothly.
         </info>
      </var>
      <var name="fildyn" type="CHARACTER" >
         <default> &apos;matdyn&apos;
         </default>
         <info> File where the dynamical matrix is written.
         </info>
      </var>
      <var name="fildrho" type="CHARACTER" >
         <default> &apos; &apos;
         </default>
         <info>
File where the charge density responses are written. Note that the file
will actually be saved as <b>${outdir}/_ph0/${prefix}.${fildrho}1</b>
where  <b>${outdir},</b> <b>${prefix}</b> and <b>${fildrho}</b> are the values of the
corresponding input variables
         </info>
      </var>
      <var name="fildvscf" type="CHARACTER" >
         <default> &apos; &apos;
         </default>
         <info>
File where the the potential variation is written
(for later use in electron-phonon calculation, see also fildrho).
         </info>
      </var>
      <var name="epsil" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. in a q=0 calculation for a non metal the
macroscopic dielectric constant of the system is
computed. Do not set <ref>epsil</ref> to .true. if you have a
metallic system or q/=0: the code will complain and stop.

Note: the input value of <ref>epsil</ref> will be ignored if <ref>ldisp</ref>=.true.
(the code will automatically set <ref>epsil</ref> to .false. for metals,
to .true. for insulators: see routine PHonon/PH/prepare_q.f90).
         </info>
      </var>
      <var name="lrpa" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. the dielectric constant is calculated at the
RPA level with DV_xc=0.
         </info>
      </var>
      <var name="lnoloc" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. the dielectric constant is calculated without
local fields, i.e. by setting DV_H=0 and DV_xc=0.
         </info>
      </var>
      <var name="trans" type="LOGICAL" >
         <default> .true.
         </default>
         <info>
If .true. the phonons are computed.
If <ref>trans</ref> .and. <ref>epsil</ref> are .true. effective charges are
calculated.
         </info>
      </var>
      <var name="lraman" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. calculate non-resonant Raman coefficients
using second-order response as in:
M. Lazzeri and F. Mauri, <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.90.036401">PRL 90, 036401 (2003)</a>.
         </info>
      </var>
      <group>
         <label> Optional variables for Raman:
         </label>
         <var name="eth_rps" type="REAL" >
            <default> 1.0d-9
            </default>
            <info> Threshold for calculation of  Pc R |psi&gt;.
            </info>
         </var>
         <var name="eth_ns" type="REAL" >
            <default> 1.0e-12
            </default>
            <info> Threshold for non-scf wavefunction calculation.
            </info>
         </var>
         <var name="dek" type="REAL" >
            <default> 1.0e-3
            </default>
            <info> Delta_xk used for wavefunction derivation wrt k.
            </info>
         </var>
      </group>
      <var name="recover" type="LOGICAL" >
         <default> .false.
         </default>
         <info> If .true. restart from an interrupted run.
         </info>
      </var>
      <var name="low_directory_check" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. search in the phsave directory only the
                 quantities requested in input.
         </info>
      </var>
      <var name="only_init" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. only the bands and other initialization quantities are calculated.
(used for GRID parallelization)
         </info>
      </var>
      <var name="qplot" type="LOGICAL" >
         <default> .false.
         </default>
         <info> If .true. a list of q points is read from input.
         </info>
      </var>
      <var name="q2d" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
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&lt; l,m &lt; 1. The weights are integer and those of points two
and three are the number of points in the two directions.
         </info>
      </var>
      <var name="q_in_band_form" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
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.
         </info>
      </var>
      <var name="electron_phonon" type="CHARACTER" >
         <default> &apos; &apos;
         </default>
         <options>
            <info>
Options are:
            </info>
            <opt val="'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.
            </opt>
            <opt val="'interpolated'" >
Electron-phonon is calculated by interpolation
over the Brillouin Zone as in M. Wierzbowska, et
al. <a href="https://arxiv.org/abs/cond-mat/0504077">arXiv:cond-mat/0504077</a>
            </opt>
            <opt val="'lambda_tetra'" >
The electron-phonon coefficient \lambda_{q \nu}
is calculated with the optimized tetrahedron method.
            </opt>
            <opt val="'gamma_tetra'" >
The phonon linewidth \gamma_{q \nu} is calculated
from the electron-phonon interactions
using the optimized tetrahedron method.
            </opt>
            <opt val="'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 &amp; B. Kozinsky,
Adv. Energy Mater. 2018, 1800246 <a href="http://dx.doi.org/10.1002/aenm.201800246">doi:10.1002/aenm.201800246</a>
<a href="https://arxiv.org/abs/1511.08115">arXiv:1511.08115</a>
            </opt>
            <opt val="'ahc'" >
Quantities required for the calculation of phonon-induced
electron self-energy are computed and written to the directory
<ref>ahc_dir</ref>. The output files can be read by postahc.x for
the calculation of electron self-energy.
Available for both metals and insulators.
<ref>trans</ref>=.false. is required.
            </opt>
            <info>
For metals only, requires gaussian smearing (except for &apos;ahc&apos;).

If <ref>trans</ref>=.true., the lambdas are calculated in the same
run, using the same k-point grid for phonons and lambdas.
If <ref>trans</ref>=.false., the lambdas are calculated using
previously saved DeltaVscf in <ref>fildvscf</ref>, previously saved
dynamical matrix, and the present punch file. This allows
the use of a different (larger) k-point grid.
            </info>
         </options>
      </var>
      <var name="el_ph_nsigma" type="INTEGER" >
         <default> 10
         </default>
         <info>
The number of double-delta smearing values used in an
electron-phonon coupling calculation.
         </info>
      </var>
      <var name="el_ph_sigma" type="REAL" >
         <default> 0.02
         </default>
         <info>
The spacing between double-delta smearing values used in
an electron-phonon coupling calculation.
         </info>
      </var>
      <group>
         <label> Variables for <ref>electron_phonon</ref> = &apos;ahc&apos;:
         </label>
         <var name="ahc_dir" type="CHARACTER" >
            <default> outdir // &apos;ahc_dir/&apos;
            </default>
            <info>
Directory where the output binary files are written.
            </info>
         </var>
         <var name="ahc_nbnd" type="INTEGER" >
            <status> REQUIRED
            </status>
            <info>
Number of bands for which the electron self-energy is to be computed.
            </info>
         </var>
         <var name="ahc_nbndskip" type="INTEGER" >
            <default> 0
            </default>
            <info>
Number of bands to exclude when computing the self-energy. Self-energy
is computed for bands with indices from <ref>ahc_nbndskip</ref>+1 to
<ref>ahc_nbndskip</ref>+<ref>ahc_nbnd</ref>. <ref>ahc_nbndskip</ref>+<ref>ahc_nbnd</ref> cannot
exceed nbnd of the preceding SCF or NSCF calculation.
            </info>
         </var>
         <var name="skip_upperfan" type="LOGICAL" >
            <default> .false.
            </default>
            <info>
If .true., skip calculation of the upper Fan self-energy, which
involves solving the Sternheimer equation.
            </info>
         </var>
      </group>
      <var name="lshift_q" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
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.
         </info>
      </var>
      <var name="zeu" type="LOGICAL" >
         <default> zeu=<ref>epsil</ref>
         </default>
         <info>
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 <ref>epsil</ref>=.true.
and <ref>zeu</ref>=.false. only the dielectric tensor is calculated.
         </info>
      </var>
      <var name="zue" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
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 <ref>trans</ref> .and. <ref>epsil</ref> )
The results should be the same within numerical noise.
         </info>
      </var>
      <var name="elop" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. calculate electro-optic tensor.
         </info>
      </var>
      <var name="fpol" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. calculate dynamic polarizabilities
Requires <ref>epsil</ref>=.true. ( experimental stage:
see example09 for calculation of methane ).
         </info>
      </var>
      <var name="ldisp" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. the run calculates phonons for a grid of
q-points specified by <ref>nq1</ref>, <ref>nq2</ref>, <ref>nq3</ref> - for direct
calculation of the entire phonon dispersion.
         </info>
      </var>
      <var name="nogg" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. disable the &quot;gamma_gamma&quot; 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.
         </info>
      </var>
      <var name="asr" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
Apply Acoustic Sum Rule to dynamical matrix, effective charges
Works only in conjunction with &quot;gamma_gamma&quot; tricks (see above)
         </info>
      </var>
      <var name="ldiag" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
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 <ref>start_irr</ref>
and <ref>last_irr</ref>. 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.
         </info>
      </var>
      <var name="lqdir" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
If .true. ph.x creates inside outdir a separate subdirectory
for each q vector. The flag is set to .true. when <ref>ldisp</ref>=.true.
and <ref>fildvscf</ref> /= &apos; &apos; or when an electron-phonon
calculation is performed. The induced potential is saved
separately for each q inside the subdirectories.
         </info>
      </var>
      <var name="search_sym" type="LOGICAL" >
         <default> .true.
         </default>
         <info>
Set it to .false. if you want to disable the mode
symmetry analysis.
         </info>
      </var>
      <vargroup type="INTEGER" >
         <var name="nq1" >
         </var>
         <var name="nq2" >
         </var>
         <var name="nq3" >
         </var>
         <default> 0,0,0
         </default>
         <info>
Parameters of the Monkhorst-Pack grid (no offset) used
when <ref>ldisp</ref>=.true. Same meaning as for nk1, nk2, nk3
in the input of pw.x.
         </info>
      </vargroup>
      <vargroup type="INTEGER" >
         <var name="nk1" >
         </var>
         <var name="nk2" >
         </var>
         <var name="nk3" >
         </var>
         <var name="k1" >
         </var>
         <var name="k2" >
         </var>
         <var name="k3" >
         </var>
         <default> 0,0,0,0,0,0
         </default>
         <info>
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.
         </info>
      </vargroup>
      <var name="diagonalization" type="CHARACTER" >
         <default> &apos;david&apos;
         </default>
         <options>
            <info>
Diagonalization method for the non-SCF calculations.
            </info>
            <opt val="'david'" >
Davidson iterative diagonalization with overlap matrix
(default). Fast, may in some rare cases fail.
            </opt>
            <opt val="'cg'" >
Conjugate-gradient-like band-by-band diagonalization.
Slower than &apos;david&apos; but uses less memory and is
(a little bit) more robust.
            </opt>
         </options>
      </var>
      <var name="read_dns_bare" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
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.
         </info>
      </var>
      <var name="ldvscf_interpolate" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
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 <ref>trans</ref> = .false..
         </info>
      </var>
      <group>
         <label> Optional variables for dvscf interpolation:
         </label>
         <var name="wpot_dir" type="CHARACTER" >
            <default> outdir // &apos;w_pot/&apos;
            </default>
            <info>
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}//&quot;1&quot;.
            </info>
         </var>
         <var name="do_long_range" type="LOGICAL" >
            <default> .false.
            </default>
            <info>
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.
            </info>
         </var>
         <var name="do_charge_neutral" type="LOGICAL" >
            <default> .false.
            </default>
            <info>
If .true., impose charge neutrality on the Born effective
charges. Used only if <ref>do_long_range</ref> = .true..
            </info>
         </var>
      </group>
      <group>
         <label> Specification of irreducible representation
         </label>
         <var name="start_irr" type="INTEGER" >
            <default> 1
            </default>
            <see> last_irr
            </see>
            <info>
Perform calculations only from <ref>start_irr</ref> to <ref>last_irr</ref>
irreducible representations.

IMPORTANT:
   * <ref>start_irr</ref> must be &lt;= 3*nat
   * do not specify <ref>nat_todo</ref> together with
     <ref>start_irr</ref>, <ref>last_irr</ref>
            </info>
         </var>
         <var name="last_irr" type="INTEGER" >
            <default> 3*nat
            </default>
            <see> start_irr
            </see>
            <info>
Perform calculations only from <ref>start_irr</ref> to <ref>last_irr</ref>
irreducible representations.

IMPORTANT:
   * <ref>start_irr</ref> must be &lt;= 3*nat
   * do not specify <ref>nat_todo</ref> together with
     <ref>start_irr</ref>, <ref>last_irr</ref>
            </info>
         </var>
         <var name="nat_todo" type="INTEGER" >
            <default> 0, i.e. displace all atoms
            </default>
            <info>
Choose the subset of atoms to be used in the linear response
calculation: <ref>nat_todo</ref> 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:
   * <ref>nat_todo</ref> &lt;= 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
            </info>
         </var>
         <var name="modenum" type="INTEGER" >
            <default> 0
            </default>
            <info>
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
&quot;modenum&quot; is not an eigenvector. What you get on output is
a column of the dynamical matrix.
            </info>
         </var>
      </group>
      <group>
         <label> q-point specification
         </label>
         <var name="start_q" type="INTEGER" >
            <default> 1
            </default>
            <see> last_q
            </see>
            <info>
Used only when ldisp=.true..
Computes only the q points from <ref>start_q</ref> to <ref>last_q</ref>.

IMPORTANT:
   * <ref>start_q</ref> must be &lt;= <ref>nqs</ref> (number of q points found)
   * do not specify <ref>nat_todo</ref> together with
     <ref>start_q</ref>, <ref>last_q</ref>
            </info>
         </var>
         <var name="last_q" type="INTEGER" >
            <default> number of q points
            </default>
            <see> start_q
            </see>
            <info>
Used only when <ref>ldisp</ref>=.true..
Computes only the q points from <ref>start_q</ref> to <ref>last_q</ref>.

IMPORTANT
   * <ref>last_q</ref> must be &lt;= <ref>nqs</ref> (number of q points)
   * do not specify <ref>nat_todo</ref> together with
     <ref>start_q</ref>, <ref>last_q</ref>
            </info>
         </var>
         <var name="dvscf_star" type="STRUCTURE" >
            <default> disabled
            </default>
            <info>
It contains the following components:

<b>dvscf_star%open</b>  (logical, default: .false.)
<b>dvscf_star%dir</b>   (character, default: outdir//&quot;Rotated_DVSCF&quot; or the
                  ESPRESSO_FILDVSCF_DIR environment variable)
<b>dvscf_star%ext</b>   (character, default: &quot;dvscf&quot;) the extension to use
                  for the name of the output files, see below
<b>dvscf_star%basis</b> (character, default: &quot;cartesian&quot;) the basis on which
                  the rotated dvscf will be saved
<b>dvscf_star%pat</b>   (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//&quot;1&quot;. 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) -&gt; q_name = &quot;0_1o2_-1o4&quot;

The dvscf can be represented on a basis of cartesian 1-atom displacements
(dvscf_star%basis=&apos;cartesian&apos;) or on the basis of the modes at the rotated q-point
(dvscf_star%basis=&apos;modes&apos;). Notice that the el-ph wannier code requires &apos;cartesian&apos;.
Each dvscf file comes with a corresponding pattern file with an additional &quot;.pat&quot;
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.
            </info>
         </var>
         <var name="drho_star" type="STRUCTURE" >
            <see> dvscf_star
            </see>
            <default> disabled
            </default>
            <info>
It contains the following components:

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

Like <ref>dvscf_star</ref>, but for the perturbation of the charge density.
Notice that the defaults are different.
            </info>
         </var>
      </group>
   </namelist>
   <choose>
      <when test="ldisp != .true.   and   qplot != .true." >
         <linecard>
            <list name="xq_list" type="REAL" >
               <format> xq(1)  xq(2)  xq(3)
               </format>
               <info>
The phonon wavevector, in units of 2pi/a0
(a0 = lattice parameter).
Not used if <ref>ldisp</ref>=.true. or <ref>qplot</ref>=.true.
               </info>
            </list>
         </linecard>
      </when>
      <elsewhen test="qplot == .true." >
         <label> Specification of q points when <ref>qplot</ref> == .true.
         </label>
         <card name="qPointsSpecs" nameless="1" >
            <syntax>
               <line>
                  <var name="nqs" type="INTEGER" >
                     <info>
Number of q points in the list. Used only if <ref>qplot</ref>=.true.
                     </info>
                  </var>
               </line>
               <table name="qPoints" >
                  <rows start="1" end="nqs" >
                     <colgroup type="REAL" >
                        <info>
q-point coordinates; used only with <ref>ldisp</ref>=.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)
                        </info>
                        <col name="xq1" >
                        </col>
                        <col name="xq2" >
                        </col>
                        <col name="xq3" >
                        </col>
                     </colgroup>
                     <col name="nq" type="INTEGER" >
                        <info>
The weight of the q-point; the meaning of nq depends
on the flags q2d and q_in_band_form.
                        </info>
                     </col>
                  </rows>
               </table>
            </syntax>
         </card>
      </elsewhen>
   </choose>
   <choose>
      <when test="nat_todo was specified" >
         <linecard>
            <list name="nat_todo_list" type="INTEGER" >
               <format> atom(1)  atom(2) ... atom(nat_todo)
               </format>
               <info>
Contains the list of indices of atoms used in the
calculation if <ref>nat_todo</ref> is specified.
               </info>
            </list>
         </linecard>
      </when>
   </choose>
   <section title=" ADDITIONAL INFORMATION " >
      <text>
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 <ref>recover</ref>=.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 <ref>recover</ref>=.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 <ref>start_irr</ref>, <ref>last_irr</ref>. 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 <ref>start_irr</ref>=0, <ref>last_irr</ref>=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, <ref>start_irr</ref> and
<ref>last_irr</ref> 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, <ref>start_irr</ref>, or <ref>last_irr</ref>.
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.
      </text>
   </section>
</input_description>