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<input_description distribution="Quantum ESPRESSO" package="PHonon" program="matdyn.x" >
   <toc>
   </toc>
   <intro>
<b>Purpose of matdyn.x:</b>

This program calculates the phonon frequencies for a list of generic
<i>q</i> vectors starting from the interatomic force constants generated
from the dynamical matrices as written by DFPT phonon code through
the companion program <b>q2r.x</b>

<b>matdyn.x</b> can generate a supercell of the original cell for mass
approximation calculation. If supercell data are not specified
in input, the unit cell, lattice vectors, atom types and positions
are read from the force constant file.

<b>Input data format:</b> [ ] = it depends

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

<b>&amp;INPUT</b>
   ...specs of the namelist variables...
<b>/</b>

[ X(1)   Y(1)   Z(1)    ityp(1)
  ...
  X(nat) Y(nat) Z(nat)  ityp(nat) ]

[ nq
  q_x(1)  q_y(1)  q_x(1)   [ nptq(1) ]
  ...
  q_x(nq) q_y(nq) q_x(nq)  [ nptq(1) ] ]
   </intro>
   <namelist name="INPUT" >
      <var name="flfrc" type="CHARACTER" >
         <info>
File produced by <b>q2r</b> containing force constants (needed)
It is the same as in the input of <b>q2r.x</b> (+ the .xml extension
if the dynamical matrices produced by ph.x were in xml
format). No default value: must be specified.
         </info>
      </var>
      <var name="asr" type="CHARACTER" >
         <default> &apos;no&apos;
         </default>
         <options>
            <info>
Indicates the type of Acoustic Sum Rule imposed.

Allowed values:
            </info>
            <opt val="'no'" >
no Acoustic Sum Rules imposed (default)
            </opt>
            <opt val="'simple'" >
previous implementation of the asr used
(3 translational asr imposed by correction of
 the diagonal elements of the force constants matrix)
            </opt>
            <opt val="'crystal'" >
3 translational asr imposed by optimized
correction of the force constants (projection)
            </opt>
            <opt val="'one-dim'" >
3 translational asr + 1 rotational asr imposed
by optimized correction of the dyn. mat. (the
rotation axis is the direction of periodicity; it
will work only if this axis considered is one of
the Cartesian axis).
            </opt>
            <opt val="'zero-dim'" >
3 translational asr + 3 rotational asr imposed
by optimized correction of the dyn. mat.
            </opt>
            <info>
Note that in certain cases, not all the rotational asr
can be applied (e.g. if there are only 2 atoms in a
molecule or if all the atoms are aligned, etc.).
In these cases the supplementary asr are cancelled
during the orthonormalization procedure (see below).
            </info>
         </options>
      </var>
      <var name="dos" type="LOGICAL" >
         <info>
if <b>.true.</b> calculate phonon Density of States (DOS)
using tetrahedra and a uniform q-point grid (see below)
<b>NB:</b> may not work properly in noncubic materials

if <b>.false.</b> calculate phonon bands from the list of q-points
supplied in input (default)
         </info>
      </var>
      <vargroup type="INTEGER" >
         <var name="nk1" >
         </var>
         <var name="nk2" >
         </var>
         <var name="nk3" >
         </var>
         <info>
uniform q-point grid for DOS calculation (includes q=0)
(must be specified if <ref>dos</ref> = .true., ignored otherwise)
         </info>
      </vargroup>
      <var name="deltaE" type="REAL" >
         <info>
energy step, in cm<sup>-1,</sup> for DOS calculation: from min
to max phonon energy (default: 1 cm<sup>-1</sup> if ndos, see
below, is not specified)
         </info>
      </var>
      <var name="ndos" type="INTEGER" >
         <info>
number of energy steps for DOS calculations
(default: calculated from deltaE if not specified)
         </info>
      </var>
      <var name="degauss" type="REAL" >
         <info>
DOS broadening in cm<sup>-1</sup>

Default: 0 - meaning use tetrahedra
         </info>
      </var>
      <var name="fldos" type="CHARACTER" >
         <info>
output file for dos (default: <tt>&apos;matdyn.dos&apos;)</tt>
the dos is in states/cm<sup>-1</sup> plotted vs omega in cm(-1)
and is normalised to 3*nat, i.e. the number of phonons
         </info>
      </var>
      <var name="flfrq" type="CHARACTER" >
         <info>
output file for frequencies (default: <tt>&apos;matdyn.freq&apos;)</tt>
         </info>
      </var>
      <var name="flvec" type="CHARACTER" >
         <info>
output file for normalized phonon displacements
(default: <tt>&apos;matdyn.modes&apos;).</tt> The normalized phonon displacements
are the eigenvectors divided by the square root of the mass,
then normalized. As such they are not orthogonal.
         </info>
      </var>
      <var name="fleig" type="CHARACTER" >
         <info>
output file for phonon eigenvectors (default: <tt>&apos;matdyn.eig&apos;)</tt>
The phonon eigenvectors are the eigenvectors of the dynamical
matrix. They are orthogonal.
         </info>
      </var>
      <var name="fldyn" type="CHARACTER" >
         <info>
output file for dynamical matrix (default: &apos; &apos; i.e. not written)
         </info>
      </var>
      <multidimension name="at" indexes="i,j" start="1,1" end="3,3" type="REAL" >
         <info>
supercell lattice vectors - must form a superlattice of the
original lattice (default: use original cell)
         </info>
      </multidimension>
      <vargroup type="INTEGER" >
         <var name="l1" >
         </var>
         <var name="l2" >
         </var>
         <var name="l3" >
         </var>
         <info>
supercell lattice vectors are original cell vectors times
l1, l2, l3 respectively (default: 1, ignored if <ref>at</ref> specified)
         </info>
      </vargroup>
      <var name="ntyp" type="INTEGER" >
         <info>
number of atom types in the supercell
(default: <ref>ntyp</ref> of the original cell)
         </info>
      </var>
      <dimension name="amass" start="1" end="ntyp" type="REAL" >
         <info>
masses of atoms in the supercell (a.m.u.), one per atom type
(default: use masses read from file <tt>flfrc)</tt>
         </info>
      </dimension>
      <var name="readtau" type="LOGICAL" >
         <info>
read  atomic positions of the supercell from input
(used to specify different masses) (default: <tt>.false.)</tt>
         </info>
      </var>
      <var name="fltau" type="CHARACTER" >
         <info>
write atomic positions of the supercell to file <tt>fltau</tt>
(default: <ref>fltau</ref> = &apos; &apos;, do not write)
         </info>
      </var>
      <var name="la2F" type="LOGICAL" >
         <info>
if <b>.true.</b> interpolates also the el-ph coefficients
         </info>
      </var>
      <var name="q_in_band_form" type="LOGICAL" >
         <info>
if <b>.true.</b> the q points are given in band form:
only the first and last point of one or more lines
are given. See below. (default: <tt>.false.).</tt>
         </info>
      </var>
      <var name="q_in_cryst_coord" type="LOGICAL" >
         <info>
if <b>.true.</b> input q points are in crystalline
coordinates (default: <tt>.false.)</tt>
         </info>
      </var>
      <var name="eigen_similarity" type="LOGICAL" >
         <info>
use similarity of the displacements to order
frequencies  (default: <tt>.false.)</tt>

<b>NB:</b> You cannot use this option with the symmetry
analysis of the modes.
         </info>
      </var>
      <var name="fd" type="LOGICAL" >
         <info>
if <b>.true.</b> the ifc come from the finite displacement calculation
         </info>
      </var>
      <var name="na_ifc" type="LOGICAL" >
         <info>
add non analitic contributions to the interatomic force
constants if finite displacement method is used (as in Wang et al.
<a href="https://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.224303">PRB 85, 224303 (2012)</a>) [to be used in conjunction with <b>fd.x]</b>
         </info>
      </var>
      <var name="nosym" type="LOGICAL" >
         <info>
if <b>.true.,</b> no symmetry and no time reversal are imposed
         </info>
      </var>
      <var name="loto_2d" type="LOGICAL" >
         <info>
set to <b>.true.</b> to activate two-dimensional treatment of LO-TO splitting
         </info>
      </var>
      <var name="loto_disable" type="LOGICAL" >
         <info>
if <b>.true.</b> do not apply LO-TO splitting for q=0
(default: <tt>.false.)</tt>
         </info>
      </var>
   </namelist>
   <choose>
      <when test="readtau == .true." >
         <card name="AtomicPositionSpecs" nameless="1" >
            <label>
if (<ref>readtau</ref>) atomic positions must be specified as follows:
            </label>
            <syntax>
               <table name="atomic_coordinates" >
                  <rows start="1" end="nat" >
                     <colgroup type="REAL" >
                        <info>
X, Y, Z atomic positions
                        </info>
                        <col name="X" >
                        </col>
                        <col name="Y" >
                        </col>
                        <col name="Z" >
                        </col>
                     </colgroup>
                     <col name="ityp" type="INTEGER" >
                        <info>
index of the atomic type
                        </info>
                     </col>
                  </rows>
               </table>
            </syntax>
         </card>
      </when>
   </choose>
   <choose>
      <when test="q_in_band_form == .true .and. dos == .false." >
         <card name="qPointsSpecs" nameless="1" >
            <label>
if (<ref>q_in_band_form</ref> .and. .not.<ref>dos</ref>) q-points must be specified as follows:
            </label>
            <syntax>
               <line>
                  <var name="nq" type="INTEGER" >
                     <info>
number of q points
                     </info>
                  </var>
               </line>
               <table name="qPoints1" >
                  <info>
The format of the q-points specification is:

(q(i,n),i=1,3), nptq

<tt>nptq</tt> is the number of points between this point
and the next. These points are automatically
generated. the q points are given in Cartesian
coordinates, 2pi/a units (a = lattice parameters)
                  </info>
                  <rows start="1" end="nq" >
                     <colgroup type="REAL" >
                        <info>
coordinates of the Q point
                        </info>
                        <col name="q_x" >
                        </col>
                        <col name="q_y" >
                        </col>
                        <col name="q_z" >
                        </col>
                     </colgroup>
                     <col name="nptq" type="INTEGER" >
                        <info>
The number of points between this point and the next.

<ref>nptq</ref> is the number of points between this point
and the next. These points are automatically
generated. the q points are given in Cartesian
coordinates, 2pi/<i>a</i> units (<i>a</i> = lattice parameters)
                        </info>
                     </col>
                  </rows>
               </table>
            </syntax>
         </card>
      </when>
      <elsewhen test="dos == .false." >
         <label>
if (.not. <ref>dos</ref>) q-points must be specified as follows:
         </label>
         <card name="qPointsSpecs" nameless="1" >
            <syntax>
               <line>
                  <var name="nq" type="INTEGER" >
                     <info>
number of q points
                     </info>
                  </var>
               </line>
               <table name="qPoints2" >
                  <info>
The format of the q-points specification is:

((q(i,n),i=1,3), n=1,nq)
                  </info>
                  <rows start="1" end="nq" >
                     <colgroup type="REAL" >
                        <info>
q-points in cartesian coordinates, 2pi/<i>a</i> units (<i>a</i> = lattice parameters)
                        </info>
                        <col name="q_x" >
                        </col>
                        <col name="q_y" >
                        </col>
                        <col name="q_z" >
                        </col>
                     </colgroup>
                  </rows>
               </table>
            </syntax>
         </card>
      </elsewhen>
   </choose>
   <section title="Notes" >
      <text>
If q = 0, the direction qhat (q=&gt;0) for the non-analytic part
is extracted from the sequence of q-points as follows:

qhat = q(n) - q(n-1)   or   qhat = q(n) - q(n+1)

depending on which one is available and nonzero.

For low-symmetry crystals, specify twice q = 0 in the list
if you want to have q = 0 results for two different directions
      </text>
   </section>
</input_description>
