<html>
  <head>
    <meta content="text/html; charset=ISO-8859-1"
      http-equiv="Content-Type">
  </head>
  <body bgcolor="#FFFFFF" text="#000000">
    <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 &eacute;crit&nbsp;:<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>
        &nbsp;<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;">
                <div dir="ltr">
                  <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">&lt;xavier.rocquefelte@cnrs-imn.fr&gt;</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">&lt;wien@zeus.theochem.tuwien.ac.at&gt;</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 &eacute;crit&nbsp;:<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 ?&nbsp; <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">&lt;xavier.rocquefelte@cnrs-imn.fr&gt;</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">&lt;wien@zeus.theochem.tuwien.ac.at&gt;</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>
                                          &nbsp;<br>
                                          <br>
                                          Le 7/9/2013 3:07 AM, Masood
                                          Yousaf a &eacute;crit&nbsp;:<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>
                                          </div>
                                          <br>
                                          <fieldset
                                            class="yiv8003400948mimeAttachmentHeader"></fieldset>
                                          <br>
                                          <pre>_______________________________________________
Wien mailing list
<a moz-do-not-send="true" rel="nofollow" class="yiv8003400948moz-txt-link-abbreviated" 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>
<a moz-do-not-send="true" rel="nofollow" class="yiv8003400948moz-txt-link-freetext" target="_blank" href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a>
SEARCH the MAILING-LIST at:  <a moz-do-not-send="true" rel="nofollow" class="yiv8003400948moz-txt-link-freetext" target="_blank" href="http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html">http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html</a>
</pre>
                                        </blockquote>
                                      </div>
                                    </div>
                                    <br>
_______________________________________________<br>
                                    Wien mailing list<br>
                                    <a moz-do-not-send="true"
                                      rel="nofollow"
                                      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>
                                    <a moz-do-not-send="true"
                                      rel="nofollow" target="_blank"
                                      href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a><br>
                                    SEARCH the MAILING-LIST at:&nbsp; <a
                                      moz-do-not-send="true"
                                      rel="nofollow" target="_blank"
href="http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html">http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html</a><br>
                                    <br>
                                    <br>
                                  </div>
                                </div>
                              </div>
                            </blockquote>
                          </div>
                        </div>
                        <br>
                        <fieldset
                          class="yiv8003400948mimeAttachmentHeader"></fieldset>
                        <br>
                        <pre>_______________________________________________
Wien mailing list
<a moz-do-not-send="true" rel="nofollow" class="yiv8003400948moz-txt-link-abbreviated" 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>
<a moz-do-not-send="true" rel="nofollow" class="yiv8003400948moz-txt-link-freetext" target="_blank" href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a>
SEARCH the MAILING-LIST at:  <a moz-do-not-send="true" rel="nofollow" class="yiv8003400948moz-txt-link-freetext" target="_blank" href="http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html">http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html</a>
</pre>
                      </blockquote>
                      <br>
                    </div>
                  </div>
                  <br>
                  _______________________________________________<br>
                  Wien mailing list<br>
                  <a moz-do-not-send="true"
                    ymailto="mailto:Wien@zeus.theochem.tuwien.ac.at"
                    href="mailto:Wien@zeus.theochem.tuwien.ac.at">Wien@zeus.theochem.tuwien.ac.at</a><br>
                  <a moz-do-not-send="true"
                    href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien"
                    target="_blank">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a><br>
                  SEARCH the MAILING-LIST at:&nbsp; <a
                    moz-do-not-send="true"
href="http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html"
                    target="_blank">http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html</a><br>
                  <br>
                  <br>
                </div>
              </div>
            </div>
          </blockquote>
        </div>
      </div>
      <br>
      <fieldset class="mimeAttachmentHeader"></fieldset>
      <br>
      <pre wrap="">_______________________________________________
Wien mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Wien@zeus.theochem.tuwien.ac.at">Wien@zeus.theochem.tuwien.ac.at</a>
<a class="moz-txt-link-freetext" href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a>
SEARCH the MAILING-LIST at:  <a class="moz-txt-link-freetext" href="http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html">http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html</a>
</pre>
    </blockquote>
    <br>
  </body>
</html>