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<div class="moz-cite-prefix">I am also using origin to determine the
absorption edge based on epsilon2. <br>
You must simply draw a tangent line along the edge and then read
the intersection between this line and "Eps2 = 0" axis. <br>
<br>
<br>
<br>
<br>
Le 7/9/2013 8:44 AM, Masood Yousaf a écrit :<br>
</div>
<blockquote
cite="mid:1373352262.99991.YahooMailNeo@web121102.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">I would be
grateful if you guide me how to apply this tangent method to the
data of imaginary part of the dielectric function. can I use
Origin to apply this ?<br>
<br>
<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;">
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<hr size="1"> <font face="Arial" size="2"> <b><span
style="font-weight:bold;">From:</span></b>
Rocquefelte <a class="moz-txt-link-rfc2396E" href="mailto:xavier.rocquefelte@cnrs-imn.fr"><xavier.rocquefelte@cnrs-imn.fr></a><br>
<b><span style="font-weight: bold;">To:</span></b> A
Mailing list for WIEN2k users
<a class="moz-txt-link-rfc2396E" href="mailto:wien@zeus.theochem.tuwien.ac.at"><wien@zeus.theochem.tuwien.ac.at></a> <br>
<b><span style="font-weight: bold;">Sent:</span></b>
Tuesday, July 9, 2013 2:30 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="yiv8003400948">
<div>
<div class="yiv8003400948moz-cite-prefix">If you
plot epsilon2 (the imaginary part of the
dielectric function) and use the tangent method,
you can estimate the absorption edge from
WIEN2K.<br>
However, it requires to use a proper functional,
allowing to overcome the inherent problems of
DFT, which is a ground state theory, i.e. LDA+U
for correlated systems or hybrid functional...<br>
<br>
Regards<br>
<br>
Xavier<br>
<br>
Le 7/9/2013 7:00 AM, Masood Yousaf a écrit :<br>
</div>
<blockquote type="cite">
<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 <a
moz-do-not-send="true"
rel="nofollow"
class="yiv8003400948moz-txt-link-rfc2396E"
ymailto="mailto:xavier.rocquefelte@cnrs-imn.fr" target="_blank"
href="mailto:xavier.rocquefelte@cnrs-imn.fr"><xavier.rocquefelte@cnrs-imn.fr></a><br>
<b><span style="font-weight:bold;">To:</span></b>
A Mailing list for WIEN2k users <a
moz-do-not-send="true"
rel="nofollow"
class="yiv8003400948moz-txt-link-rfc2396E"
ymailto="mailto:wien@zeus.theochem.tuwien.ac.at" target="_blank"
href="mailto:wien@zeus.theochem.tuwien.ac.at"><wien@zeus.theochem.tuwien.ac.at></a>
<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="yiv8003400948y_msg_container"><br>
<div id="yiv8003400948">
<div>
<div
class="yiv8003400948moz-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 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>
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