<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<blockquote
cite="mid:BN3PR0501MB1170471DBCDFA842A3DA841280B00@BN3PR0501MB1170.namprd05.prod.outlook.com"
type="cite">
<div id="divtagdefaultwrapper"
style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;">
<p>I am now doing optical properties calculation for
semimetals. I have a few question related to the energy shift
in case.inkram file. If I don't do energy shift, I can't get a
reasonable results compared to experiments. That brings me
into two questions.</p>
<div><br>
</div>
<div>First, what is energy shift here? </div>
</div>
</blockquote>
<br>
It is a correction to the DFT band gap. Refer to:<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.wien2k.at/events/ws2006/Optics_Vienna_April_2006.pdf">http://www.wien2k.at/events/ws2006/Optics_Vienna_April_2006.pdf</a>
(slide 16)<br>
<a class="moz-txt-link-freetext" href="http://etsf.polytechnique.fr/sites/default/files/dft-II-silva.pdf">http://etsf.polytechnique.fr/sites/default/files/dft-II-silva.pdf</a>
(slide 8)<br>
<a class="moz-txt-link-freetext" href="http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg13017.html">http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg13017.html</a><br>
<br>
<blockquote
cite="mid:BN3PR0501MB1170471DBCDFA842A3DA841280B00@BN3PR0501MB1170.namprd05.prod.outlook.com"
type="cite">
<div id="divtagdefaultwrapper"
style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;">
<div>How do you determine whether you need energy shift or not?</div>
</div>
</blockquote>
<br>
Compare the calculated and experimental results. If they match, you
don't need it.<br>
<br>
<blockquote
cite="mid:BN3PR0501MB1170471DBCDFA842A3DA841280B00@BN3PR0501MB1170.namprd05.prod.outlook.com"
type="cite">
<div id="divtagdefaultwrapper"
style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;"><span
style="font-size: 12pt;">Second,how do you determine the exact
number of shift, is it shown in some file?</span></div>
</blockquote>
<br>
There are two methods used to apply the scissors operator (energy
shift): the first is to set it so that the DFT band gap matches with
the measured band gap before the optical calculation and the second
is two perform the optical calculation followed by adjusting it in
subsequent calculations until the calculated result (major peak)
aligns with the measured one. The later approach is usually used.
From page 196 in:<br>
<br>
<i>Density Functional Theory of Molecules, Clusters, and Solids</i>,
2nd Ed., D. E. Ellis, Ed., Springer Netherlands, 1996:
<a class="moz-txt-link-freetext" href="http://link.springer.com/book/10.1007%2F978-94-011-0487-6">http://link.springer.com/book/10.1007%2F978-94-011-0487-6</a> .<br>
</body>
</html>