?Dear PWScf Users,
I did the band structure of? BN (zinc blende) with two atoms and I found a
indirect gap? (like literature) Gamma-X. But when I did it with 8 atoms I found
direct gap Gamma -Gamma.
Normally if we change (nat = 2, ibrav = 2) to (nat = 8, ibrav = 1),we find the
same nature of gap.
If such we have the composition B0.25Ga0.75N how we can determine the nature of
gap?
?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
bests
Said Asma
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