<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"> <br><div id="yiv1374445898"><div><div style="color:#000;background-color:#fff;font-family:times new roman, new york, times, serif;font-size:12pt;"><div class="yiv1374445898yui_3_2_0_19_133473943415454" id="yiv1374445898yui_3_2_0_19_133473943415456" style="font-family:times new roman, new york, times, serif;font-size:12pt;"><div id="yiv1374445898yui_3_2_0_19_133473943415479" class="yiv1374445898yui_3_2_0_19_133473943415461" style="font-family:times new roman, new york, times, serif;font-size:12pt;">Dear PWScf Users,<br><br><span id="result_box" class="" lang="en"><span class="hps">I did the</span> <span class="hps">band structure</span> <span class="hps">of</span> </span><span id="result_box" class="" lang="en"> <span class="hps">BN</span></span><span id="result_box" class="" lang="en"> <span class="hps">(zinc</span> <span
class="hps">blende</span><span class="hps"></span>) <span class="hps">with two</span> <span class="hps">atoms</span> <span class="hps">and I found</span> <span class="hps">a</span></span><span id="result_box" class="" lang="en"><span class="hps"> indirect</span></span><span id="result_box" class="" lang="en"> <span class="hps">gap</span> <span class="hps"></span> <span class="hps atn">(</span><span>like</span> <span class="hps">literature</span><span>)</span> <span class="hps">Gamma</span><span class="atn">-</span><span>X.</span> But <span class="hps">when</span> <span class="hps">I did it</span> <span class="hps">with 8</span> <span class="hps">atoms</span> <span class="hps">I found</span> <span class="hps">direct gap</span> <span class="hps">Gamma</span> -<span class="hps">Gamma</span><span class="atn"></span></span>.<br><br>Why such a problem occurs?<br><br>My input files is as following:<br> <br> *With TWO ATOMS:<br><br>cat >
bn.band.in << EOF<br> &control<br> calculation='bands'<br> pseudo_dir = '$PSEUDO_DIR/',<br> outdir='$TMP_DIR/',<br> prefix='bn'<br> /<br> &system<br> ibrav= 2, celldm(1) = 6.76, nat= 2, ntyp= 2,<br> ecutwfc = 60.0,<br> occupations ='smearing',<br> smearing = 'methfessel-paxton',<br> degauss= 0.03,<br> /<br> &electrons<br> conv_thr = 1.0d-7 ,<br> mixing_mode = 'plain' ,<br> mixing_beta = 0.2
,<br> diagonalization = 'david' ,<br> /<br>ATOMIC_SPECIES<br> B 10.811 B.pz-vbc.UPF<br> N 14.007 N.pz-vbc.UPF<br>ATOMIC_POSITIONS<br> B 0.00 0.00 0.00<br> N 0.25 0.25 0.25<br>K_POINTS {crystal_b}<br>5<br>0.5 0.5 0.5 400<br>0 0 0 400<br>1.0 0 0 400<br>0.75 0.75 0 400<br>0 0 0 400<br>EOF<br>$ECHO " running the band-structure calculation for bn...\c"<br>$PW_COMMAND < bn.band.in > bn.band.out<br>check_failure $?<br>$ECHO " done"<br><br><br><br>*and WITH 8 ATOMS:<br><br>cat > bn.band.in << EOF<br>
&control<br>
calculation='bands'<br>
pseudo_dir = '$PSEUDO_DIR/',<br>
outdir='$TMP_DIR/',<br>
prefix='bn'<br>
/<br>
&system<br>
ibrav= 1, celldm(1) = 6.82, nat=8, ntyp= 2,<br>
ecutwfc = 40.0, nbnd = 40,<br>
occupations ='smearing',<br>
smearing = 'methfessel-paxton',<br>
degauss= 0.02,<br>
/<br>
&electrons<br>
conv_thr = 1.0d-7,<br>
mixing_beta = 0.2,<br>
/<br>
<br>
ATOMIC_SPECIES<br>
B 10.811 B.pz-vbc.UPF<br>
N 14.007 N.pz-vbc.UPF<br>
ATOMIC_POSITIONS<br>
B 0.000 0.000 0.000<br>
N 0.250 0.250 0.250<br>
B 0.000 0.500 0.500<br>
N 0.250 0.750 0.750<br>
B 0.500 0.500 0.000<br>
N 0.750 0.250 0.750<br>
B 0.500 0.000 0.500<br>
N 0.750 0.750 0.250<br>
<br>
K_POINTS {crystal_b}<br>
4<br>
0 0 0 40<br>
0.5 0 0 40<br>
0.5 0.5 0 40<br>
0 0 0 40<br>
EOF<br>
$ECHO " running the band-structure calculation for bn...\c"<br>
$PW_COMMAND < bn.band.in > bn.band.out<br>
check_failure $?<br>
$ECHO " done"<br><br>Any help would be appreciated.<br>Best regards,<br>Said Asma<br><br> </div> </div> </div></div></div></div></body></html>