# Input File Description

## Program: q2r.x / PHonon / Quantum ESPRESSO (version: 7.2)

> ### TABLE OF CONTENTS

> > INTRODUCTION

> > &INPUT

> > > fildyn | flfrc | zasr | loto_2d | write_lr

> > Line-of-input: nr1 | nr2 | nr3

> > fileSpecs

> > > nfile | file

> ### INTRODUCTION

> >     Purpose of q2r.x:

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

> >     Input data format: [ ] = it depends

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

> >     &INPUT
> >        ...specs of namelist variables...
> >     /

> >     [ nr1 nr2 nr3
> >       nfile
> >          file(1)
> >          file(2)
> >          ...
> >          file(nfile) ]

## Namelist: &INPUT

fildyn | CHARACTER
Status: | REQUIRED

>     Input file name (must be specified).

>     "fildyn"0 contains information on the q-point grid

>     "fildyn"1-N contain force constants C_n = C(q_n),
>          where n = 1,...N, 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 ph.x are in .xml format. In this case
>     fildyn is the same as in the phonon code + the
>     .xml extension.

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flfrc | CHARACTER
Status: | REQUIRED

>     Output file containing the IFC in real space (must be specified)

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zasr | CHARACTER
Default: | 'no'

>     Indicates the type of Acoustic Sum Rules used for the Born
>     effective charges.

>     Allowed values:

> `'no' :`

>       no Acoustic Sum Rules imposed (default)

> `'simple' :`

>       previous implementation of the asr used
>       (3 translational asr imposed by correction of
>        the diagonal elements of the force-constants matrix)

> `'crystal' :`

>       3 translational asr imposed by optimized
>       correction of the IFC (projection)

> `'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).

> `'zero-dim' :`

>       3 translational asr + 3 rotational asr
>       imposed by optimized correction of the IFC.

>     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).

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loto_2d | LOGICAL

>     set to .true. to activate two-dimensional treatment
>     of LO-TO splitting.

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write_lr | LOGICAL
Default: | `.false.`

>     set to .true. to write long-range IFC into q2r IFC file.
>     This is required when enforcing asr='all' for infrared-
>     active solids in matdyn. An additional column will be written
>     for long-range part of IFC for text format, while a tag named
>     IFC_LR will be created for xml format.

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IF `file {fildyn}0 does not exist :`

>     If a file "fildyn"0 is not found, the code will ignore variable
>     fildyn and will try to read from the following cards the missing
>     information on the q-point grid and file names:

> ### Line of input

> ### Syntax:

> > nr1 nr2 nr3

> ### Description of items:

> > nr1, nr2, nr3 | INTEGER

> > >     dimensions of the FFT grid formed by the q-point grid

> > [Back to Top]

> ## Card: fileSpecs

> ### Syntax:

> > nfile

> > file(1)
> > file(2)
> > . . .
> > file(nfile)

> ### Description of items:

> > nfile | INTEGER

> > >     number of files containing C(q_n), n=1,nfile

> > [Back to Top]

> > file | CHARACTER

> > >     names of the files containing C(q_n), n=1,nfile

> > >     Note that the name and order of files is not important as
> > >     long as q=0 is the first.

> > [Back to Top]

This file has been created by helpdoc utility on Sat Mar 18 19:08:13 CET 2023.