<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div><span>Dear Layla,</span></div><div><span id="result_box" class="" lang="en"><span class="hps">Thank you</span> <span class="hps">for your</span> <span class="hps">answer</span><span>,</span> <span class="hps">normally if</span> <span class="hps">we change</span> <span class="hps atn">(</span><span>nat</span> <span class="hps">= 2</span><span>,</span> <span class="hps">ibrav</span> <span class="hps">=</span> <span class="hps">2)</span> <span class="hps">to</span> <span class="hps atn">(</span><span class="">nat</span> <span class="hps">= 8</span><span>,</span> <span class="hps">ibrav</span> <span class="hps">=</span> <span class="hps">1)</span>,<span class="hps">we find</span> <span class="hps">the same</span> <span class="hps">nature</span> <span class="hps">of gap</span><span>.</span><br> <span class="hps">If</span> <span
class="hps">such</span> <span class="hps alt-edited">we have</span> <span class="hps">the composition</span> <span class="hps">B0.25Ga0.75N</span> <span class="hps alt-edited">how we can</span> <span class="hps">determine</span> <span class="hps">the nature of</span> <span class="hps">gap?</span></span></div><div><br><span id="result_box" class="" lang="en"><span class="hps"></span></span></div><div>bests</div><div><br></div><div>Said Asma<br></div><div><br></div> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div dir="ltr"> <font size="2" face="Arial"> <hr size="1"> <b><span style="font-weight:bold;">De :</span></b> Layla Martin-Samos <lmartinsamos@gmail.com><br> <b><span style="font-weight: bold;">À :</span></b> Said Asma <saidasma1987@yahoo.fr> <br><b><span style="font-weight: bold;">Cc :</span></b>
"pw_forum@pwscf.org" <pw_forum@pwscf.org> <br> <b><span style="font-weight: bold;">Envoyé le :</span></b> Mercredi 18 avril 2012 15h45<br> <b><span style="font-weight: bold;">Objet :</span></b> Re: [Pw_forum] (no subject)<br> </font> </div> <br><div id="yiv503455836">Dear Said, it is not a problem, I think, as increasing the number of atoms will fold the Brillouin zone into gamma. <br><br>bests<br><br>Layla<br><br><div class="yiv503455836gmail_quote">2012/4/18 Said Asma <span dir="ltr"><<a rel="nofollow" ymailto="mailto:saidasma1987@yahoo.fr" target="_blank" href="mailto:saidasma1987@yahoo.fr">saidasma1987@yahoo.fr</a>></span><br>
<blockquote class="yiv503455836gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;"><div><div style="font-size:12pt;font-family:times new roman, new york, times, serif;"> <br><div><div><div style="font-size:12pt;font-family:times new roman, new york, times, serif;">
<div style="font-family:times new roman, new york, times, serif;font-size:12pt;"><div style="font-family:times new roman, new york, times, serif;font-size:12pt;">Dear PWScf Users,<br><br><span lang="en"><span>I did the</span> <span>band structure</span> <span>of</span> </span><span lang="en"> <span>BN</span></span><span lang="en"> <span>(zinc</span> <span>blende</span><span></span>) <span>with two</span> <span>atoms</span> <span>and I found</span> <span>a</span></span><span lang="en"><span> indirect</span></span><span lang="en"> <span>gap</span> <span></span> <span>(</span><span>like</span> <span>literature</span><span>)</span> <span>Gamma</span><span>-</span><span>X.</span> But <span>when</span> <span>I did it</span> <span>with 8</span> <span>atoms</span> <span>I found</span> <span>direct gap</span> <span>Gamma</span> -<span>Gamma</span><span></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 >
<a rel="nofollow" target="_blank" href="http://bn.band.in">bn.band.in</a> << 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 < <a rel="nofollow" target="_blank" href="http://bn.band.in">bn.band.in</a> > bn.band.out<br>
check_failure $?<br>$ECHO " done"<br><br><br><br>*and WITH 8 ATOMS:<br><br>cat > <a rel="nofollow" target="_blank" href="http://bn.band.in">bn.band.in</a> << 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 < <a rel="nofollow" target="_blank" href="http://bn.band.in">bn.band.in</a> > 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></div><br>_______________________________________________<br>
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