SeqQuest band structure example

This band structure example and associated scripts was developed by Andrew C. Pineda (AFRL),
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Table of Contents

  1. Setting up the band structure calculation
  2. CdS Band structure
  3. Quest input file

Setting up the band structure calculation

To set up a band structure calculation, first you do a single-point SeqQuest calculation, configuring the band structure calculation using the options specified in the band structure manual. The input file to generate the CdS band structure, along a user-specified set of branches, is below.

At the conclusion of the run, the code generates two files needed to plot the band structure:

These files can be used to plot a band structure using a visualization tool such as Grace/XMGrace. A Perl script that combines these two files into a usable plot using Grace/XMGrace is available here. This script includes options for adding labels. The figure below presents an example output from the script. The dashed line in the figure represents the Fermi level output by the code. In this figure, the Fermi level has been shifted to zero using the capabilities of Grace/XMGrace.

Example band structure for CdS

CdSBandsExample.png

Example SeqQuest input file to generate CdS band structure

output level
4
do setup
do iters
no force
no relax
do post
no cell
do bands
setup data
notes 
 CdS (Fd-3m)(sg 227) FINAL RELAXED CELL ENERGY =     -113.1589305653
end_notes
functional
 PBE
dimension of system (0=cluster ... 3=bulk)
 3
coordinates
lattice
primitive lattice vectors
  0.0000000000        5.6252238919        5.6252238919
  5.6252238919        0.0000000000        5.6252238919
  5.6252238919        5.6252238919        0.0000000000
grid dimensions
  36 36 36
atom types
  2
atom file
/home/acpineda/QUEST/atmlib-27jun07/pbe/Cd.atm
atom file
/home/acpineda/QUEST/atmlib-27jun07/pbe/S.atm
number of atoms in unit cell
   2
atom, type, position vector
   1    1   0.00000000000   0.00000000000   0.00000000000
   2    2   0.25000000000   0.25000000000   0.25000000000
kgrid
 8 8 8
symops - for symmetry group #  227
 3
definitions of symmetry operations
-4   0.00000   0.00000   1.00000      0.00000   0.00000   0.00000
 3   1.00000   1.00000   1.00000      0.00000   0.00000   0.00000  
-2   1.00000   1.00000   0.00000      0.00000   0.00000   0.00000 
end setup phase data
run phase input data
cutfrc - extends cutoffs for force calculations, to get better stress
 5.d-2
convergence criterion
 0.000010
geometry parameters
gblend
 0.42
gsteps
 50
gconv  - max force convergence criterion
 0.0001
end geometry data
bandstructure input
bravais lattice
fc2
nbranch
5
symbol labels
GX
XW
WL
LG
GK
end bandstructure input
end of run phase data
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Send questions and comments to: Peter Schultz at paschul@sandia.gov
Last updated: February 22, 2014