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<p class="Standard"><span lang="EN-US"><br></span></p><p class="Standard"><span lang="EN-US">I did the band structure of AlAs (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.<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">Why such a problem occurs?<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US" style="mso-ascii-font-family:Calibri;
mso-ascii-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:
minor-latin;mso-bidi-font-family:Calibri;mso-bidi-theme-font:minor-latin;
color:#2A2A2A;background:white;mso-ansi-language:EN-US">Thank you for your help
and advice.</span><span lang="EN-US"><o:p></o:p></span></p>
<p class="Standard"><span style="background-color: white; color: rgb(42, 42, 42); font-size: 10pt; ">This is the
input file for the "nscf" calculation</span></p>
<p class="Standard"><span lang="EN-US" style="background-color: white; background-position: initial initial; background-repeat: initial initial; "><br></span></p><p class="Standard"><span lang="EN-US" style="background-color: white; background-position: initial initial; background-repeat: initial initial; ">With TWO ATOMS:</span><span lang="EN-US"><o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"><br></span></p><p class="Standard"><span lang="EN-US"> &control<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">
calculation='nscf'<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">
restart_mode='from_scratch',<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> tstress =
.true.<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> tprnfor =
.true.<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">
prefix='820-28',<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> pseudo_dir =
'/home/test/pseudo/',<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">
outdir='/home/test/tp/'<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> /<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> &system<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> ibrav= 2, celldm(1) =10.64, nat= 2, ntyp= 2,<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> ecutwfc
=50.0, ecutrho = 200.0, nbnd =8,<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> /<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> &electrons<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">
diagonalization='david'<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> conv_thr =
1.0e-7<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> mixing_beta
= 0.7<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> /<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">ATOMIC_SPECIES<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> al 26.9815 al_pz.upf<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> as 74.9216 as_pz.upf<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">ATOMIC_POSITIONS<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> al 0.00 0.00 0.00<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> as 0.250 0.250 0.250<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">K_POINTS<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 20<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.0000 0.5000
1.0000 1<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.1000 0.5000
0.9000 2<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.2000
0.5000 0.8000 3<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.3000
0.5000 0.7000 4<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.4000
0.5000 0.6000 5<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.5000
0.5000 0.5000 6<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.4000
0.4000 0.4000 7<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.3000 0.3000
0.3000 8<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.1000
0.1000 0.1000 9</span></p><p class="Standard"><span style="font-size: 10pt; "> </span><span style="font-size: 10pt; ">0.0000</span><span style="font-size: 10pt; "> </span><span style="font-size: 10pt; ">0.0000</span><span style="font-size: 10pt; ">
</span><span style="font-size: 10pt; ">0.0000</span><span style="font-size: 10pt; "> </span><span style="font-size: 10pt; ">10</span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 0.1000 11<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 0.2000 12<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 0.3000 13<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 0.4000 14<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 0.5000 15<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.0000 0.6000
16<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 0.7000 17<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 0.8000 18<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 0.9000 19<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">0.0000
0.0000 1.0000 20<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US" style="background-color: white; background-position: initial initial; background-repeat: initial initial; "><o:p> </o:p></span></p>
<p class="Standard"><span lang="EN-US" style="background-color: white; background-position: initial initial; background-repeat: initial initial; ">and WITH 8 ATOMS:</span><span lang="EN-US"><o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"><br></span></p><p class="Standard"><span lang="EN-US">&control<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">
calculation='nscf'<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">
restart_mode='from_scratch',<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> tstress =
.true.<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> tprnfor = .true.<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> prefix='820-28',<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> pseudo_dir = '/home/test/pseudo/',<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> outdir='/home/test/tp/'<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> /<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> &system<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> ibrav=
1, celldm(1) =10.64, nat= 8,
ntyp= 2,<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> ecutwfc =50.0, ecutrho = 200.0, nbnd =32,<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> /<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> &electrons<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> diagonalization='david'<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> conv_thr = 1.0e-7<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> mixing_beta = 0.7<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> /<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">ATOMIC_SPECIES<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> al 26.9815
al_pz.upf<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> as 74.9216
as_pz.upf<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">ATOMIC_POSITIONS
<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">al 0.00000000
0.00000000 0.00000000<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">al 0.50000000
0.50000000 0.00000000<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">al 0.50000000
0.00000000 0.50000000<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">al 0.00000000 0.50000000
0.50000000<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">as 0.25000000
0.25000000 0.25000000<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">as 0.75000000
0.75000000 0.25000000<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">as 0.75000000
0.25000000 0.75000000<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">as 0.25000000
0.75000000 0.75000000<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US">K_POINTS<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 16<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> 0.5000
0.5000 0.5000 1</span></p>
<p class="Standard"><span lang="EN-US">0.4000 0.4000
0.4000 2</span></p>
<p class="Standard"><span lang="EN-US">0.3000 0.3000
0.3000 3</span></p>
<p class="Standard"><span lang="EN-US">0.2000 0.2000
0.2000 4</span></p>
<p class="Standard"><o:p> </o:p></p>
<p class="Standard"><span lang="EN-US"> 0.1000
0.1000 0.1000 5</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.0000
0.0000 6</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.0000
0.1000 7</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.0000
0.2000 8</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.0000
0.3000 9</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.0000
0.4000 10</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.0000
0.5000 11</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.1000
0.5000 12</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.2000
0.5000 13</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.3000
0.5000 14</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.4000
0.5000 15</span></p>
<p class="Standard"><span lang="EN-US">0.0000 0.5000
0.5000 16<o:p></o:p></span></p>
<p class="Standard"><span lang="EN-US"> </span></p>
<p class="ecxmsonormal" style="margin-top:0cm;margin-right:0cm;margin-bottom:
16.2pt;margin-left:0cm;background:white"><span style="font-family:"Verdana","sans-serif";
mso-bidi-font-family:"Segoe UI";color:#2A2A2A">***********************************************************</span><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#2A2A2A"><br>
</span><span style="font-size:10.0pt;font-family:"Arial","sans-serif";
color:#2A2A2A">Ramzi Alaya</span><span style="font-size:10.0pt;font-family:
"Segoe UI","sans-serif";color:#2A2A2A"><o:p></o:p></span></p>
<p class="Standard"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";
color:#2A2A2A;background:white">E-mail : ramzialaya@hotmail.fr<br>
Faculté des Sciences de Gabès, Cité Erriadh 6072 Gabès- Tunisie<br>
Unité de Recherche sur les Hétéro-Epitaxies et Applications</span></p> </div></body>
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