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<div class="moz-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>
</div>
<blockquote
cite="mid:1373332068.32620.YahooMailNeo@web121104.mail.ne1.yahoo.com"
type="cite">
<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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