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<DIV><FONT face=Arial size=2>I have tried calculating the band-gap of Ge in a
similar way to example01 for Si, and obtained a direct band-gap=0.75, indirect
band-gap=0.46 at a lattice constant=10.614 (optimized lattice constant,
converged ecutwfc). At the experimental lattice constant the direct
band-gap=0.51, indirect band-gap=0.38. In literature the band-gaps for LDA are
quoted as being negative. Why am I getting positive results? Is there a problem
with the pseudopotential? I noticed from the archives that in July 2004
this issue was raised, but an answer wasn't really given. Thank you very
much for your help,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Dr. Helen Eisenberg,</FONT></DIV>
<DIV><FONT face=Arial size=2><FONT size=3>Post-doctoral researcher,<BR>The Fritz
Haber Center for Molecular Dynamics,<BR>The Hebrew University of
Jerusalem,<BR>Jerusalem 91904 Israel</FONT> </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>INPUT:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>&control<BR> calculation =
'scf'<BR> restart_mode='from_scratch',<BR>
prefix='ge',<BR> tstress = .true.<BR>
tprnfor = .true.<BR> pseudo_dir =
'$PSEUDO_DIR/',<BR>
outdir='$TMP_DIR/'<BR> /<BR> &system
<BR> ibrav= 2, celldm(1) =10.6769, nat= 2, ntyp=
1,<BR> ecutwfc =27.0,
<BR> /<BR> &electrons<BR>
diagonalization=cg<BR> mixing_mode =
'plain'<BR> mixing_beta = 0.7 <BR> conv_thr
= 1.0d-8<BR> /<BR>ATOMIC_SPECIES<BR> Ge 72.59
Ge.pz_bhs.UPF<BR>ATOMIC_POSITIONS<BR> Ge 0.00 0.00 0.00 <BR> Ge 0.25
0.25 0.25 <BR>K_POINTS<BR> 10<BR> 0.1250000
0.1250000 0.1250000 1.00<BR> 0.1250000
0.1250000 0.3750000 3.00<BR> 0.1250000
0.1250000 0.6250000 3.00<BR> 0.1250000
0.1250000 0.8750000 3.00<BR> 0.1250000
0.3750000 0.3750000 3.00<BR> 0.1250000
0.3750000 0.6250000 6.00<BR> 0.1250000
0.3750000 0.8750000 6.00<BR> 0.1250000
0.6250000 0.6250000 3.00<BR> 0.3750000
0.3750000 0.3750000 1.00<BR> 0.3750000
0.3750000 0.6250000 3.00<BR>EOF<BR> $ECHO
" running the scf calculation for Si...\c"<BR>
$PW_COMMAND < ge.scf.cg.in > ge.scf.cg.out<BR> $ECHO "
done"</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> # band structure calculation
along delta, sigma and lambda lines<BR> cat > ge.band.cg.in
<< EOF<BR> &control<BR>
calculation='bands'
<BR> pseudo_dir = '$PSEUDO_DIR/',<BR>
outdir='$TMP_DIR/',<BR>
prefix='ge'<BR> /<BR> &system
<BR> ibrav= 2, celldm(1) =10.6769, nat= 2, ntyp=
1,<BR> ecutwfc =27.0, nbnd =
8,<BR> /<BR> &electrons
<BR>
diagonalization=cg<BR> /<BR>ATOMIC_SPECIES<BR> Ge 72.59
Ge.pz_bhs.UPF<BR>ATOMIC_POSITIONS<BR> Ge 0.00 0.00 0.00 <BR> Ge 0.25
0.25 0.25 <BR>K_POINTS<BR> 6<BR> 0.0 0.0 0.0
1.0<BR> 0.1 0.1 0.1 1.0<BR> 0.2 0.2 0.2
1.0<BR> 0.3 0.3 0.3 1.0<BR> 0.4 0.4 0.4
1.0<BR> 0.5 0.5 0.5 1.0</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>EOF:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>RESULTS:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> k
= 0.0000 0.0000 0.0000 band energies (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> -7.1507
5.4288 5.4288 5.4288 5.9790
8.0294 8.0294 8.0294</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2> k = 0.1000 0.1000
0.1000 band energies (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> -7.0370
3.6667 5.2082 5.2082 6.8127
8.3334 8.3334 8.6989</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2> k = 0.2000 0.2000
0.2000 band energies (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> -6.7011
1.6617 4.7838 4.7838 6.5618
8.8874 8.8874 10.4632</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2> k = 0.3000 0.3000
0.3000 band energies (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> -6.1690
-0.1311 4.4065 4.4065 6.1730
9.1840 9.1840 12.2437</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2> k = 0.4000 0.4000
0.4000 band energies (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> -5.5394
-1.5375 4.1640 4.1640 5.9087
9.1822 9.1822 12.7544</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2> k = 0.5000 0.5000
0.5000 band energies (ev):</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> -5.1829
-2.1557 4.0814 4.0814 5.8180
9.1444 9.1444 12.6631<BR></FONT></DIV></BODY></HTML>