# Input File Description ## Program: bands.x / PWscf / Quantum Espresso (version: 6.6)
> > ### TABLE OF CONTENTS INTRODUCTION &BANDS prefix | outdir | filband | spin_component | lsigma | lp | filp | lsym | no_overlap | plot_2d | firstk | lastk ### INTRODUCTION
> >     Purpose of bands.x:
> >        Re-order bands, computes band-related properties. Currently,
> >        re-ordering can be done with two different algorithms:
> >        (a) by maximising the overlap with bands at previous k-point
> >        (b) by computing symmetry properties of each wavefunction
> >        Bands-related properties that can be computed are currently
> >        (a) The expectation value of the spin operator on each spinor
> >            wave-function (noncolinear case only)
> >        (b) The expectation value of p

> >     The input data can be read from standard input or from file using
> >     command-line options "bands.x -i file-name" (same syntax as for pw.x)

> >     Output files:
> >     - file filband containing the band structure, in a format
> >       suitable for plotting code "plotband.x"
> >     - file "filband".rap (if lsym is .t.)  with symmetry information,
> >       to be read by plotting code "plotband.x"
> >     - if (lsigma(i)): file "filband".i, i=1,2,3, with expectation values
> >       of the spin operator in the noncolinear case
> >     - file "filband".gnu with bands in eV, directly plottable using gnuplot
> >     - file filp with matrix elements of p

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

> >        &BANDS
> >          ...
> >        /
## Namelist: &BANDS
prefix | CHARACTER
Default: | 'pwscf'
>     prefix of files saved by program pw.x
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outdir | CHARACTER
Default: | value of the ESPRESSO_TMPDIR environment variable if set; current directory ('./') otherwise
>     directory containing the input data, i.e. the same as in pw.x
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filband | CHARACTER
Default: | 'bands.out'
>     file name for band output (to be read by "plotband.x")
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spin_component | INTEGER
>     In the lsda case select:

>        1 = spin-up
>        2 = spin-down
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lsigma(i), i=1,3 | LOGICAL
>     If true computes expectation values of the spin operator
>     on the spinor wave-functions (only in the noncollinear case),
>     writes them to a file "filband".i, i=1,2,3
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lp | LOGICAL
Default: | .false.
>     If .true. matrix elements of the momentum operator p between
>     conduction and valence bands are computed and written to file
>     specified in filp
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filp | CHARACTER
Default: | 'p_avg.dat'
>     If lp is set to .true., file name for matrix elements of p
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lsym | LOGICAL
Default: | .true.
>     If .true. the bands are classified according to the
>     irreducible representations of the small group of k.
>     A file "filband".rap with the same format of "filband"
>     is written, for usage by "plotband.x"
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no_overlap | LOGICAL
Default: | .true.
>     If .false., and if lsym is .false., writes the eigenvalues
>     in the order that maximises overlap with the neighbor k-points
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plot_2d | LOGICAL
Default: | .false.
>     If .true. writes the eigenvalues in the output file
>     in a 2D format readable by gnuplot. Band ordering is not
>     changed. Each band is written in a different file called
>     filband.# with the format:

>        xk, yk, energy
>        xk, yk, energy
>        ..  ..  ..

>     energies are written in eV and xk in units 2\pi/a.
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firstk, lastk | INTEGER
>     if lsym=.true. makes the symmetry analysis only for k
>     points between firstk to lastk
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This file has been created by helpdoc utility on Fri Jul 17 10:28:28 CEST 2020.