Hello everyone,
I am wondering how to extract the matrix elements from the valence bands
to the conduction bands at the Brillouin zone center, Gamma point in
Quantum espresso.
I tried to calculate the matrix elements of Si and I got the result in
the p_avg.dat. But it looks weird, because the the corresponding matrix
elements along x, y ,z directions (for example, three values |/M/_11 |^2
along x.y,z directions) are totally different shown below.
*&p_mat nbnd= 6, nks= 29 /
0.000000 0.000000 0.000000 4
1
0.00022045 0.02823071 0.03700090 0.13449672
0.00458980 0.00203767 0.00400515 0.00964742
2
0.00327610 0.02056865 0.04947954 0.00093171
0.00019941 0.07363126 0.09566180 0.03136617
3
0.00146403 0.07631971 0.06399219 0.00701410
0.00016914 0.00944635 0.02901511 0.16348040*
Because Si has face-centered cubic crystal structure and the matrix
elements located at the same positions along x, y, z directions should
be same, right?
My general calculation procedures are shown below:
*1. run scf.in*
&control
calculation = 'scf'
restart_mode='from_scratch'
prefix = 'si'
outdir = './outdir'
pseudo_dir = '/home/yyb/qe-7.0/pseudo'
/
&system
ibrav=2, celldm(1) =10.410909236,
nat=2, ntyp=1,
ecutwfc=40
ecutrho=320
nbnd=6
occupations='smearing', smearing='gaussian',degauss=0.005
!nosym = .true.
!noinv = .true.
!occupations = 'fixed'
!input_dft = 'gaupbe'
!nqx1 = 4, nqx2 = 4, nqx3 = 4,
!x_gamma_extrapolation = .false.
! exxdiv_treatment = 'none'
/
&electrons
conv_thr=1e-10
/
ATOMIC_SPECIES
Si 28.0855 Si_ONCV_PBE-1.0.upf
ATOMIC_POSITIONS (alat)
Si 0.00 0.00 0.00
Si 0.25 0.25 0.25
K_POINTS (automatic)
8 8 8 0 0 0
*2.run bands.x*
&bands
outdir='./outdir/'
prefix='si'
filband='si.bands.dat'
lp=.true.
filp = 'p_avg.dat'
/
I don't know how to get the right result and could anyone who has the
experience give me some help or suggestions?_______________________________________________
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