<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt">Dear Sir, thanks for your elaboration. Need some further explanation to overcome the confusion. Is it possible to determine accurately absorption edge from WIEN2k code only i.e., from case.epsilon ? <br><div><br></div><div>Best wishes<br>Masood<br><br> <blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; margin-top: 5px; padding-left: 5px;"> <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"> <hr size="1"> <font face="Arial" size="2"> <b><span style="font-weight:bold;">From:</span></b> Rocquefelte <xavier.rocquefelte@cnrs-imn.fr><br> <b><span style="font-weight: bold;">To:</span></b> A Mailing list for WIEN2k users <wien@zeus.theochem.tuwien.ac.at> <br>
<b><span style="font-weight: bold;">Sent:</span></b> Tuesday, July 9, 2013 12:40 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [Wien] How to calculate optical absorption edge ?<br> </font> </div> <div class="y_msg_container"><br><div id="yiv2164697746">
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<div class="yiv2164697746moz-cite-prefix">Experimentally an absorption edge
(optical gap) is estimated using the tangent method. <br>
Thus you should do the same with your calculated data to compare
optical gap values, which differ from a fundamental band gap. <br>
<br>
Indeed, a fundamental band gap is the smallest band gap allowing
to excite an electron in unoccupied states (deduced from
electrical measurements - thus no transition rules). <br>
In contrast, the optical gap is related to an excitation using
photons, thus it respects the dipolar transitions rules (this gap
is usually larger than the fundamental band gap). <br>
<br>
Regards<br>
<br>
Xavier<br>
<br>
<br>
Le 7/9/2013 3:07 AM, Masood Yousaf a écrit :<br>
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<div style="color:#000;background-color:#fff;font-family:times new roman, new york, times, serif;font-size:12pt;">Dear wien2k
users<br>
<br>
Kindly suggest how to calculate optical absortion edge in wien2k
? How it differs from band gap of material ? I read that first
critical point in imaginary part of the dielectric function
represents optical absorption edge. But how to ensure that which
is the first critical point. Kindly guide<br>
<br>
<div>Best wishes<br>
Masood<br>
Universiti Tecknologi Malaysia<br>
</div>
</div>
<br>
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