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<input_description distribution="Quantum ESPRESSO" package="PHonon" program="q2r.x" >
   <toc>
   </toc>
   <intro>
<b>Purpose of q2r.x:</b>

It reads force constant matrices C(q) produced by the <b>ph.x</b> code
for a grid of q-points and calculates the corresponding set
of interatomic force constants (IFC), C(R)

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

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

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

[ nr1 nr2 nr3
  nfile
     file(1)
     file(2)
     ...
     file(nfile) ]
   </intro>
   <namelist name="INPUT" >
      <var name="fildyn" type="CHARACTER" >
         <status> REQUIRED
         </status>
         <info>
Input file name (must be specified).

<b>&quot;fildyn&quot;0</b> contains information on the q-point grid

<b>&quot;fildyn&quot;1-N</b> contain force constants C_n = C(q_n),
     where <b>n = 1,...N</b>, where N is the number of
     q-points in the irreducible brillouin zone.

Normally this should be the same as specified on input
to the phonon code.

In the non collinear/spin-orbit case the files
produced by <b>ph.x</b> are in .xml format. In this case
<ref>fildyn</ref> is the same as in the phonon code + the
.xml extension.
         </info>
      </var>
      <var name="flfrc" type="CHARACTER" >
         <status> REQUIRED
         </status>
         <info>
Output file containing the IFC in real space (must be specified)
         </info>
      </var>
      <var name="zasr" type="CHARACTER" >
         <default> &apos;no&apos;
         </default>
         <options>
            <info>
Indicates the type of Acoustic Sum Rules used for the Born
effective charges.

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 IFC (projection)
            </opt>
            <opt val="'one-dim'" >
3 translational asr + 1 rotational asr
imposed by optimized correction of the IFC (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 IFC.
            </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="loto_2d" type="LOGICAL" >
         <info>
set to <b>.true.</b> to activate two-dimensional treatment
of LO-TO splitting.
         </info>
      </var>
   </namelist>
   <choose>
      <when test="file {fildyn}0 does not exist" >
         <message>
If a file <b>&quot;fildyn&quot;0</b> is not found, the code will ignore variable
<ref>fildyn</ref> and will try to read from the following cards the missing
information on the q-point grid and file names:
         </message>
         <linecard>
            <vargroup type="INTEGER" >
               <var name="nr1" >
               </var>
               <var name="nr2" >
               </var>
               <var name="nr3" >
               </var>
               <info>
dimensions of the FFT grid formed by the q-point grid
               </info>
            </vargroup>
         </linecard>
         <card name="fileSpecs" nameless="1" >
            <syntax>
               <line>
                  <var name="nfile" type="INTEGER" >
                     <info>
number of files containing C(q_n), n=1,<ref>nfile</ref>
                     </info>
                  </var>
               </line>
               <table name="file_n" >
                  <rows start="1" end="nfile" >
                     <col name="file" type="CHARACTER" >
                        <info>
names of the files containing C(q_n), n=1,<ref>nfile</ref>

Note that the name and order of files is not important as
long as <b>q=0 is the first</b>.
                        </info>
                     </col>
                  </rows>
               </table>
            </syntax>
         </card>
      </when>
   </choose>
</input_description>
