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<p>Hello everyone,</p>
<p>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.</p>
<p>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, <span
style="font-size: 12pt; line-height: 107%; color: black;">three
values </span><!--[if gte mso 9]><xml>
<o:OfficeDocumentSettings>
<o:AllowPNG/>
</o:OfficeDocumentSettings>
</xml><![endif]--><span style="color:black;mso-themecolor:text1">|<i
style="mso-bidi-font-style:normal">M</i><sub>11</sub>|<sup>2</sup></span><span
style="font-size:14.0pt;line-height:107%;font-family:"Times New Roman",serif;
color:black;mso-themecolor:text1;background:white"></span><span
style="font-size: 12pt; line-height: 107%; color: black;">along
x.y,z directions)</span> are totally different shown below.</p>
<p><b>&p_mat nbnd= 6, nks= 29 /<br>
0.000000 0.000000 0.000000 4<br>
1<br>
0.00022045 0.02823071 0.03700090 0.13449672<br>
0.00458980 0.00203767 0.00400515 0.00964742<br>
2<br>
0.00327610 0.02056865 0.04947954 0.00093171<br>
0.00019941 0.07363126 0.09566180 0.03136617<br>
3<br>
0.00146403 0.07631971 0.06399219 0.00701410<br>
0.00016914 0.00944635 0.02901511 0.16348040</b><br>
</p>
<p>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?</p>
<p>My general calculation procedures are shown below: </p>
<p><b>1. run scf.in</b></p>
<p>&control<br>
calculation = 'scf'<br>
restart_mode='from_scratch'<br>
prefix = 'si'<br>
outdir = './outdir'<br>
pseudo_dir = '/home/yyb/qe-7.0/pseudo'<br>
/<br>
&system<br>
ibrav=2, celldm(1) =10.410909236, <br>
nat=2, ntyp=1,<br>
ecutwfc=40<br>
ecutrho=320<br>
nbnd=6<br>
occupations='smearing', smearing='gaussian',degauss=0.005<br>
!nosym = .true.<br>
!noinv = .true.<br>
!occupations = 'fixed'<br>
!input_dft = 'gaupbe'<br>
!nqx1 = 4, nqx2 = 4, nqx3 = 4,<br>
!x_gamma_extrapolation = .false.<br>
! exxdiv_treatment = 'none'<br>
/<br>
&electrons<br>
conv_thr=1e-10<br>
/<br>
ATOMIC_SPECIES<br>
Si 28.0855 Si_ONCV_PBE-1.0.upf<br>
<br>
ATOMIC_POSITIONS (alat)<br>
Si 0.00 0.00 0.00<br>
Si 0.25 0.25 0.25<br>
K_POINTS (automatic)<br>
8 8 8 0 0 0 <br>
</p>
<p><b>2.run bands.x</b></p>
<p>&bands<br>
outdir='./outdir/'<br>
prefix='si'<br>
filband='si.bands.dat'<br>
lp=.true.<br>
filp = 'p_avg.dat'<br>
/<br>
</p>
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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