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 (including the nonlocal potential
contribution i*m*[V_nl,x])
Structure of the input data:
============================
&BANDS
...
/
'pwscf'
prefix of files saved by program pw.x
directory containing the input data, i.e. the same as in pw.x
value of the ESPRESSO_TMPDIR environment variable if set;
current directory ('./') otherwise
'bands.out'
file name for band output (to be read by "plotband.x")
In the lsda case select:
1 = spin-up
2 = spin-down
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
.false.
If .true. matrix elements of the momentum operator p between
conduction and valence bands are computed and written to file
specified in [filp].
The matrix elements include the contribution from the nonlocal
potential, i*m*[V_nl, x]. In other words, the calculated matrix elements
are those of the velocity operator i*m*[H, x] times mass, not those of
the true momentum operator.
'p_avg.dat'
If [lp] is set to .true., file name for matrix elements of p
.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"
.true.
If .false., and if [lsym] is .false., writes the eigenvalues
in the order that maximises overlap with the neighbor k-points
.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.
if [lsym]=.true. makes the symmetry analysis only for k
points between firstk to lastk