Dear PWScf Users,
I did the band structure of?BN(zinc blende) with two atoms and I found
aindirectgap? (like literature) Gamma-X. But when I did it with 8 atoms I found
direct gap Gamma -Gamma.
Why such a problem occurs?
My input files is as following:
?
?*With TWO ATOMS:
cat > bn.band.in << EOF
?&control
??? calculation='bands'
??? pseudo_dir = '$PSEUDO_DIR/',
??? outdir='$TMP_DIR/',
??? prefix='bn'
?/
?&system
??? ibrav=? 2, celldm(1) = 6.76, nat=? 2, ntyp= 2,
??? ecutwfc = 60.0,
??? occupations ='smearing',
??? smearing = 'methfessel-paxton',
??? degauss= 0.03,
?/
?&electrons
???????????????? conv_thr = 1.0d-7 ,
???????????????? mixing_mode = 'plain' ,
???????????????? mixing_beta = 0.2 ,
???????????????? diagonalization = 'david' ,
?/
ATOMIC_SPECIES
?B? 10.811? B.pz-vbc.UPF
?N? 14.007? N.pz-vbc.UPF
ATOMIC_POSITIONS
? B 0.00 0.00 0.00
? N 0.25 0.25 0.25
K_POINTS {crystal_b}
5
0.5? 0.5? 0.5? 400
0??? 0??? 0??? 400
1.0? 0??? 0??? 400
0.75 0.75 0??? 400
0??? 0??? 0??? 400
EOF
$ECHO "? running the band-structure calculation for bn...\c"
$PW_COMMAND < bn.band.in > bn.band.out
check_failure $?
$ECHO " done"
*and WITH 8 ATOMS:
cat > bn.band.in << EOF
?&control
??? calculation='bands'
??? pseudo_dir = '$PSEUDO_DIR/',
??? outdir='$TMP_DIR/',
??? prefix='bn'
?/
?&system
??? ibrav= 1, celldm(1) = 6.82, nat=8, ntyp= 2,
??? ecutwfc = 40.0, nbnd = 40,
??? occupations ='smearing',
??? smearing = 'methfessel-paxton',
??? degauss= 0.02,
?/
?&electrons
? conv_thr =? 1.0d-7,
??? mixing_beta = 0.2,
?/
ATOMIC_SPECIES
?B? 10.811? B.pz-vbc.UPF
?N? 14.007? N.pz-vbc.UPF
ATOMIC_POSITIONS
?B????? 0.000???? 0.000???? 0.000
?N????? 0.250???? 0.250???? 0.250
?B????? 0.000???? 0.500???? 0.500
?N????? 0.250???? 0.750???? 0.750
?B????? 0.500???? 0.500???? 0.000
?N????? 0.750???? 0.250???? 0.750
?B????? 0.500???? 0.000???? 0.500
?N????? 0.750???? 0.750???? 0.250
K_POINTS {crystal_b}
4
0??? 0??? 0??? 40
0.5? 0??? 0??? 40
0.5? 0.5? 0??? 40
0??? 0??? 0??? 40
EOF
$ECHO "? running the band-structure calculation for bn...\c"
$PW_COMMAND < bn.band.in > bn.band.out
check_failure $?
$ECHO " done"
Any help would be appreciated.
Best regards,
Said Asma
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