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input_description -distribution {Quantum Espresso} -package PWscf -program bands.x {
toc {}
intro {
@b {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 @ref filband containing the band structure, in a format
suitable for plotting code "plotband.x"
- file "filband".rap (if @ref lsym is .t.) with symmetry information,
to be read by plotting code "plotband.x"
- if (@ref 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 @ref filp with matrix elements of p
@b {Structure of the input data:}
============================
@b &BANDS
...
@b /
}
namelist BANDS {
var prefix -type CHARACTER {
default {'pwscf'}
info {
prefix of files saved by program pw.x
}
}
var outdir -type CHARACTER {
info {
directory containing the input data, i.e. the same as in pw.x
}
default {
value of the ESPRESSO_TMPDIR environment variable if set;
current directory ('./') otherwise }
}
var filband -type CHARACTER {
default {'bands.out'}
info {
file name for band output (to be read by "plotband.x")
}
}
var spin_component -type INTEGER {
info {
In the lsda case select:
1 = spin-up
2 = spin-down
}
}
dimension lsigma -start 1 -end 3 -type LOGICAL {
info {
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
}
}
var lp -type LOGICAL {
default { .false. }
info {
If .true. matrix elements of the momentum operator p between
conduction and valence bands are computed and written to file
specified in @ref filp
}
}
var filp -type CHARACTER {
default { 'p_avg.dat' }
info {
If @ref lp is set to .true., file name for matrix elements of p
}
}
var lsym -type LOGICAL {
default { .true. }
info {
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"
}
}
var no_overlap -type LOGICAL {
default { .true. }
info {
If .false., and if @ref lsym is .false., writes the eigenvalues
in the order that maximises overlap with the neighbor k-points
}
}
var plot_2d -type LOGICAL {
default { .false. }
info {
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:
@i {
xk, yk, energy
xk, yk, energy
.. .. ..
}
energies are written in eV and xk in units 2\pi/a.
}
}
vargroup -type INTEGER {
var firstk
var lastk
info {
if @ref lsym=.true. makes the symmetry analysis only for k
points between firstk to lastk
}
}
}
}
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