<div>Dear Professor Eyvaz:</div><div>Thank you very much for your instruction:)</div><div><br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div><div style="font-family:times new roman,new york,times,serif;font-size:12pt"><div class="im">>When q is zero, there is no longitude and transverse mode. <br></div>Really? How about optical modes? Did you pay attention to "O"? <br>
</div></div></blockquote><div>I do not express myself clearly.</div><div>When q=0, q has no direction. Therefore, optical modes can not be classified into longitude or transverse ones. As a result, at q=0, these optical phonon should be still degenerate( LO=TO ).</div>
<div> </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div><div style="font-family:times new roman,new york,times,serif;font-size:12pt"><div class="im">
Bests,<br>Eyvaz.
<br><div> </div>-------------------------------------------------------------------<br>Prof. Eyvaz Isaev, <br>Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden <br>Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, <br>
<a href="mailto:isaev@ifm.liu.se" target="_blank">isaev@ifm.liu.se</a>, <a href="mailto:eyvaz_isaev@yahoo.com" target="_blank">eyvaz_isaev@yahoo.com</a><div><br></div></div><div style="font-family:times new roman,new york,times,serif;font-size:12pt">
<br><div style="font-family:times new roman,new york,times,serif;font-size:12pt"><font face="Tahoma" size="2"><hr size="1"><div class="im"><b><span style="font-weight:bold">From:</span></b> xirainbow <<a href="mailto:nkxirainbow@gmail.com" target="_blank">nkxirainbow@gmail.com</a>><br>
</div><div class="im"><b><span style="font-weight:bold">To:</span></b> PWSCF Forum <<a href="mailto:pw_forum@pwscf.org" target="_blank">pw_forum@pwscf.org</a>><br></div><b><span style="font-weight:bold">Sent:</span></b> Fri, April 29, 2011 9:30:31 AM<div class="im">
<br><b><span style="font-weight:bold">Subject:</span></b> Re: [Pw_forum] LO-TO splitting in dynmat.x<br></div></font><div><div></div><div class="h5"><br>
<div>Dear Sonu Kumar</div><div>What you said is reasonable;)</div><div><br></div><div>I have two little questions.</div><div>One:</div><div><span style="font-family:arial,sans-serif;font-size:12.5px;border-collapse:collapse">Does LO-TO splitting must disappear at the boundary of Brillouin zone?</span></div>
<div><br></div><div>Two:</div><div>I can understand the LO-TO splitting near Gamma point.</div><div>However, at Gamma point(not near Gamma point), q=0. When q is zero, there is no longitude and transverse mode. Why are there LO-TO splitting at Gamma point?</div>
<div><br></div><div>Thanks:)</div><div><br></div><br><br><div class="gmail_quote">On Fri, Apr 29, 2011 at 1:21 PM, sonu kumar <span dir="ltr"><<a rel="nofollow" href="mailto:1009ukumar@gmail.com" target="_blank">1009ukumar@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex">Dear All QE users,<br><br>i am sorry again, as i havn't corrected the subject title.<div><br>
<br>
<blockquote class="gmail_quote" style="border-left:1px solid rgb(204, 204, 204);margin:0pt 0pt 0pt 0.8ex;padding-left:1ex">(2) only cubic crystals has LO and TO braches.<br></blockquote>
<div> </div></div><div class="gmail_quote"><div>crystals ( having considerable values of macroscopic dielectric constant [ i suppose<br>epsilon
infinity] and born effective charges, as pointed out by Prof. Eyvaz
Isaev) with low symmetry can, also, have LO-TO splitting. But this can
be different in different symmetry directions, so one has to search
all symmetry directions for this splitting.<br>
<br>For cubic crystals splitting is equal in all directions.<br></div></div><br>with regards,<br clear="all"><font color="#888888"><br>-- <br>Sonu Kumar<br><br>Phd Student<br>Physics Department<br>Indian Institute of Technology <br>
Delhi-110016, India<br><span>
web:-<a href="http://www.iitd.ac.in/" target="_blank">http://www.iitd.ac.in/</a></span><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>____________________________________<br>Hui Wang<br>School of physics, Fudan University, Shanghai, China<br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>____________________________________<br>Hui Wang<br>School of physics, Fudan University, Shanghai, China<br>