?Dear Giannozzi ,
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 (the unit cell has changed to simple cubic).
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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