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3.6 what='scf_bands'

With this option the code makes a self-consistent calculation followed by a band structure calculation. This option is not parallelized over images and should be used with one image. The output of the band structure calculation is further processed in order to produce a plot of the band structure. The zero of the energy is the highest valence band of the first k point in insulators and the Fermi energy in metals.
The energy bands plot can be modified by the following variables:

emin_input : minimum energy for the band dispersion plot (in eV).
             Default: real minimum of the bands
emax_input : maximum energy for the band dispersion plot (in eV).
             Default: real maximum of the bands
nbnd_bands : the number of bands in the band calculation.
             Default: integer 2*nbnd, where nbnd is the number 
             of bands given in pw.x input or calculated by pw.x.
only_bands_plot: if the files with the bands and the represen-
             tations are already on files, this option allows to 
             change the parameters of the plot (such as the 
             maximum or minimum energy) and do another plot 
             without additional calculation. If the files are
             missing and this variable is .TRUE. an error 
             occurs. Note that using this option you cannot 
             change the path.
             Default: logical .FALSE.
lsym       : if .TRUE. does the symmetry analysis of the bands.
             Default: .TRUE.
enhance_plot: if .TRUE. writes on the band plot the point 
             group labels, and colors with different background 
             colors lines at the zone border.
             Default: .FALSE.
long_path  : if .TRUE. plots the bands in all the Brillouin 
             zone path. Otherwise makes a faster calculation 
             on a short path. The short path is indicated also 
             for two-dimensional layers perpendicular to the 
             z direction.
             Default: .TRUE.
old_path   : if .TRUE. use an alternative path, usually more 
             similar to the one used in experimental papers 
             (available only for a few lattices).
             Default: .FALSE.
path_fact  : A factor that multiply the number of points along 
             each line of the default path. Note that this is 
             a real number so you can also decrease the default 
             number of points along each line.
             Default: real 1.0
filband    : file where the bands are written in the QE format.
             Default: character(len=*) 'output_band.dat'
flpband    : file(s) where the bands are written in gnuplot 
             Default: character(len=*) 'output_pband.dat'
flpsband   : postscript file with the electronic band structure.
             Default: character(len=*) 'output_band'

Number of tasks for this option: 1.

By default, the bands are plotted along a fixed path in the Brillouin zone, but the user can modify this behavior giving the path at the end of the INPUT_THERMO namelist with the same format used for the pw.x input. The automatic path generation is not available for base-centered monoclinic and for triclinic Bravais lattices. For these lattices the path must be given explicitly. The following variables control the path:

q_in_band_form   : only the first and last point of each k 
                 path are given. The weight of each k point 
                 is an integer, the number of points in the 
                 line that starts at this k point.
                 Default: logical .TRUE.
q_in_cryst_coord : the k - points are given in crystal 
                 coordinates. For centered lattices the 
                 crystal coordinates refer to the primitive 
                 cell (not the conventional one). Same 
                 convention as in QE.
                 Default: logical .FALSE.
point_label_type : the label definition (see the BZ manual).
                 Default: SC
q2d              : the q points define a rectangle in 
                 reciprocal space. See the QE guide for 
                 more details.
                 Default: logical .FALSE.
is_a_path        : if .TRUE. the q points are in a path in 
                 reciprocal space. This is usually the case 
                 except when q2d=.TRUE. or when the input 
                 points are in an arbitrary order. Set this 
                 to .FALSE. only if you want to skip the plot 
                 of the bands.
                 Default: logical .TRUE.

Note that the path is not given in the input of pw.x that contain instead the information to generate the mesh of k points for the self-consistent calculation. An example for this option can be found in example02. If you give explicitly the path, be careful with options that require geometry changes (see below). Only automatic paths, or path given through letter labels are easily recalculated. The other paths could turn out to be correct only for one geometry.

It is also possible to separate the self-consistent and the band calculation, by running first thermo_pw.x using what='scf' and then running, on the same directory, thermo_pw.x using what='scf_bands'. The same input can be used in the two calculations, only the thermo_control file need to be changed. The number or processors and pools can be changed in the same cases in which this is possible in pw.x. You cannot however run twice thermo_pw.x on the same directory using what='scf_bands' and two different paths, you must use two different working directories.

next up previous contents
Next: 3.7 what='scf_2d_bands' Up: 3. Input variables Previous: 3.5 what='scf_nk'   Contents