Dear Said, I have not a big experience in crystals but as long as I understand, the "nature" of the gap is defined by its "nature" calculated with the unit cell of your crystal. If instead of the unit cell you are using bigger cells then you need to make a careful analysis of the symmetries to unfold your brilloin zone by hand. When you use dopants, is the same mechanism. To be safe and avoid manual unfoldings, you need to build the unit cell corresponding to B0.25Ga075N. I have no idea of what is the unit cell for your system. Maybe you can find more info in crystallographic tables.<br>
<br>best regards<br><br>Layla<br><br><div class="gmail_quote">2012/4/18 Said Asma <span dir="ltr"><<a href="mailto:saidasma1987@yahoo.fr">saidasma1987@yahoo.fr</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div style="font-size:12pt;font-family:times new roman,new york,times,serif"><div><span>Dear Layla,</span></div><div><span lang="en"><span>Thank you</span> <span>for your</span> <span>answer</span><span>,</span> <span>normally if</span> <span>we change</span> <span>(</span><span>nat</span> <span>= 2</span><span>,</span> <span>ibrav</span> <span>=</span> <span>2)</span> <span>to</span> <span>(</span><span>nat</span> <span>= 8</span><span>,</span> <span>ibrav</span> <span>=</span> <span>1)</span>,<span>we find</span> <span>the same</span> <span>nature</span> <span>of gap</span><span>.</span><br>
<span>If</span> <span>such</span> <span>we have</span> <span>the composition</span> <span>B0.25Ga0.75N</span> <span>how we can</span> <span>determine</span> <span>the nature of</span> <span>gap?</span></span></div><div><br>
<span lang="en"><span></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 face="Arial"> <hr size="1"> <b><span style="font-weight:bold">De :</span></b> Layla Martin-Samos <<a href="mailto:lmartinsamos@gmail.com" target="_blank">lmartinsamos@gmail.com</a>><br> <b><span style="font-weight:bold">À :</span></b> Said Asma <<a href="mailto:saidasma1987@yahoo.fr" target="_blank">saidasma1987@yahoo.fr</a>> <br>
<b><span style="font-weight:bold">Cc :</span></b>
"<a href="mailto:pw_forum@pwscf.org" target="_blank">pw_forum@pwscf.org</a>" <<a href="mailto:pw_forum@pwscf.org" target="_blank">pw_forum@pwscf.org</a>> <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>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>2012/4/18 Said Asma <span dir="ltr"><<a rel="nofollow" href="mailto:saidasma1987@yahoo.fr" target="_blank">saidasma1987@yahoo.fr</a>></span><br>
<blockquote 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" href="http://bn.band.in" target="_blank">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" href="http://bn.band.in" target="_blank">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" href="http://bn.band.in" target="_blank">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" href="http://bn.band.in" target="_blank">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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<br></blockquote></div><br>
</div><br><br> </div> </div> </div></div></blockquote></div><br>