<html><body><div style="color:#000; background-color:#fff; font-family:verdana, helvetica, sans-serif;font-size:13px"><div dir="ltr" id="yui_3_16_0_1_1442595054707_9287"><span>Dear Dr. Alias,</span></div><div id="yui_3_16_0_1_1442595054707_9448" dir="ltr"><br><span></span></div><div id="yui_3_16_0_1_1442595054707_9447" dir="ltr"><span id="yui_3_16_0_1_1442595054707_9505">Thank you very much for the explanation.</span></div><div id="yui_3_16_0_1_1442595054707_9446" dir="ltr"><br><span></span></div><div id="yui_3_16_0_1_1442595054707_9445" dir="ltr"><span id="yui_3_16_0_1_1442595054707_9504">Please what really cause these excitations since we're dealing with the ground state properties?<br></span></div><div id="yui_3_16_0_1_1442595054707_9288"><div id="yui_3_16_0_1_1442595054707_9636"> </div><div id="yui_3_16_0_1_1442595054707_9683">Any comment in this regard is highly appreciated.</div><div id="yui_3_16_0_1_1442595054707_9709"><br></div></div><div id="yui_3_16_0_1_1442595054707_9290" class="signature"><div id="yui_3_16_0_1_1442595054707_9289"><font id="yui_3_16_0_1_1442595054707_9292" face="verdana, helvetica, sans-serif" size="3"><i id="yui_3_16_0_1_1442595054707_9291">Lawal Mohammed</i></font></div><br> </div><br><div id="yui_3_16_0_1_1442595054707_9297" style="font-family: verdana, helvetica, sans-serif; font-size: 13px;"> <div id="yui_3_16_0_1_1442595054707_9296" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_1_1442595054707_9295" dir="ltr"> <hr id="yui_3_16_0_1_1442595054707_9527" size="1"> <font id="yui_3_16_0_1_1442595054707_9503" face="Arial" size="2"> <b><span style="font-weight:bold;">From:</span></b> Elias Assmann <elias.assmann@gmail.com><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> Friday, September 18, 2015 6:56 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [Wien] Optic<br> </font> </div> <div id="yui_3_16_0_1_1442595054707_9299" class="y_msg_container"><br>-----BEGIN PGP SIGNED MESSAGE-----<br clear="none">Hash: SHA1<br clear="none"><div class="qtdSeparateBR"><br><br></div><div class="yqt6742638985" id="yqtfd32921"><br clear="none">On 09/15/2015 08:36 PM, Lawal Mohammed wrote:<br clear="none">> I understand that in gga/lda the Kohn-Sham eigenstates are regarded<br clear="none">> as excited only when the scissors operator is non zero, is this<br clear="none">> correct? If yes then how valid is optical calculation when the<br clear="none">> scissors operator is set to zero? If no then what bring about the<br clear="none">> optical excitations that allow determination of some optical<br clear="none">> properties?</div><br clear="none"><br clear="none">The “scissors operator” is simply a rigid shift of the unoccupied<br clear="none">bands in energy (where rigid means that the states themselves are not<br clear="none">changed). This is done to “correct” band gaps which come out wrong<br clear="none">(usually too small) in DFT. An optical excitation takes an electron<br clear="none">from an occupied to an unoccupied state. This means that the scissors<br clear="none">operator will change the energies where these excitations are<br clear="none">possible, e.g. to adjust the optical gap in your calculation to the<br clear="none">experimental value.<br clear="none"><br clear="none">HTH,<br clear="none"><br clear="none"> Elias<br clear="none"><br clear="none"><br clear="none">-----BEGIN PGP SIGNATURE-----<br clear="none">Version: GnuPG v1<br clear="none">Comment: Using GnuPG with Icedove - <a shape="rect" href="http://www.enigmail.net/" target="_blank">http://www.enigmail.net/</a><br clear="none"><br clear="none">iQIcBAEBAgAGBQJV++3ZAAoJEE/4gtQZfOqPKvEP/Rn5QZqwVZcNdtlAsl9OiWVl<br clear="none">49pkLhtV98TuuXnItDvI/1kzcuQrggK2vvCgfXpu2zD7RE2eP6sUBfMTSsB7/Rlh<br clear="none">duCESsliMt/LBFU+vwxBhEEF4zJu0MQrQ5Tb6Pnl1LUb+2YvaoVCL1e3nNfPP1iU<br clear="none">5so5Db3MVnGpNiiTRtiSvTCnUj6z0tALao6pvegzob5w/HOaIqMeY7pcPZBymnaY<br clear="none">uobcaXnscCPd75omhLXwsRIvynRfXgTblcxU3ld5242EEZRzg0wtkUJoSYKQsQVJ<br clear="none">t4DUUbO+tsn3wgsZOaJPZ8X79lvUOcgb/7MO/DbP+tXVhAzxjx3sD+Tnx0wqRU+V<br clear="none">p/HPpN7Eu3YzekCqtc6kTE9szX9CKjYWFhpMItqnRfKQTcNbDtkJLexm/XbUu/W7<br clear="none">WpgHoQVWmgYmLGwMLP3rZvH+oGHCqFHfHxxcMou9Bq8Oj44ul35alP3qZcvaJ7gp<br clear="none">nceY+cXbsnuacaiTc4WqF/qc92EwYuKJoRkF8kcHj2YnrFoJTiHuFS8dtsH4Juwn<br clear="none">4Vq/NUPNVliL1XFKnCeBYqaQk6Gi8g6kgFRKDS/mU3RuTDNzvO/KEECG5Of1VB3j<br clear="none">rg82hbszX4ZW07d4V05Yg1UNJeRypJ8ZLYmMLeiK+HrJ4HONHnq4WopLmWqht1I0<br clear="none">Yv2ikdHGRyXn7rwghXqQ<br clear="none">=BART<br clear="none">-----END PGP SIGNATURE-----<br clear="none">_______________________________________________<br clear="none">Wien mailing list<br clear="none"><a shape="rect" ymailto="mailto:Wien@zeus.theochem.tuwien.ac.at" href="mailto:Wien@zeus.theochem.tuwien.ac.at">Wien@zeus.theochem.tuwien.ac.at</a><br clear="none"><a shape="rect" href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien" target="_blank">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a><br clear="none">SEARCH the MAILING-LIST at: <a shape="rect" 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></div> </div> </div> </div></body></html>