<div dir="ltr">Dear Paolo,<div><br></div><div>Using the following input, I did two calculations, once at gamma point only, and once with 4 4 3 0 0 0 K-sampling, to calculate the bandgap of ZnS (a semiconductor with a direct gap at gamma point)</div>
<div><br></div><div><div>/</div><div>&SYSTEM</div><div> ibrav = 4</div><div> A = 3.811</div><div> C = 6.234</div><div> nat = 4</div><div> ntyp = 2</div>
<div> nbnd = 19</div><div> ecutwfc = 80</div><div>/</div><div>&ELECTRONS</div><div>/</div><div>ATOMIC_SPECIES</div><div> Zn 65.409 Zn.pbe-nc.UPF</div><div> S 32.066 S.pbe-n-nc.UPF</div><div>ATOMIC_POSITIONS crystal</div>
<div> Zn 0.33333 0.66667 0.000</div><div> Zn 0.66667 0.33333 0.500</div><div> S 0.33333 0.66667 0.375</div><div> S 0.66667 0.33333 0.875</div><div>K_POINTS automatic OR K_POINTS gamma</div><div> 4 4 3 0 0 0</div>
</div><div><br></div><div><br></div><div>For gamma only calculation, I have the following band energies:</div><div><br></div><div><div> k = 0.0000 0.0000 0.0000 ( 3194 PWs) bands (ev):</div><div> -5.6961 -4.6015 -0.1027 -0.1027 -0.0711 -0.0495 -0.0495 0.2414</div>
<div> 0.2414 0.3243 0.3243 0.5610 1.6809 6.5472 6.5474 7.4256</div><div> 7.5926 7.5926 9.2391</div></div><div><div> highest occupied, lowest unoccupied level (ev): 7.5926 9.2391</div>
</div>
<div><br></div><div><br></div><div>For 4 4 3 0 0 0 sampling, I got the followings:</div><div><br></div><div><div>k = 0.0000 0.0000 0.0000 ( 6387 PWs) bands (ev):</div><div> -6.6872 -5.7232 0.0468 0.0574 0.0574 0.1373 0.1373 0.4912</div>
<div> 0.4913 0.5680 0.5680 0.7323 1.1728 5.6554 5.6556 6.5171</div><div> 6.5888 6.5888 8.6817</div></div><div><div> highest occupied, lowest unoccupied level (ev): 6.5888 8.6817</div>
</div>
<div><br></div><div><br></div><div><br></div><div>In both cases the gap occurs at gamma point, however, the numbers are different. How should I explain this?</div><div><br></div><div>Thanks in advance,</div><div><br></div>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Dec 19, 2012 at 5:41 AM, Paolo Giannozzi <span dir="ltr"><<a href="mailto:giannozz@democritos.it" target="_blank">giannozz@democritos.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im"><br>
On Dec 19, 2012, at 11:28 , Giuseppe Mattioli wrote:<br>
<br>
> Always negligible experimental measurements (i.e., vox populi)? :-)<br>
<br>
</div>experiments are made on real semiconductors, not on theoretical<br>
ones ...<br>
<div class="HOEnZb"><div class="h5"><br>
P.<br>
---<br>
Paolo Giannozzi, Dept of Chemistry&Physics&Environment,<br>
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>
Phone <a href="tel:%2B39-0432-558216" value="+390432558216">+39-0432-558216</a>, fax <a href="tel:%2B39-0432-558222" value="+390432558222">+39-0432-558222</a><br>
<br>
<br>
<br>
<br>
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Amin Torabi<br>Ph.D. student<br>Chemistry Dept.<br>The University of Western Ontario<br>London, On Canada, N6A 5B7<br><span style="font-family:'Droid Sans',arial,sans-serif;font-size:13px;border-collapse:collapse;color:rgb(32,32,32)">Phone: <a value="+15196612111" style="color:rgb(103,117,58)">519-661-2111</a> Ext: 87871</span><div>
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