<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">well, you probably know more than I do, but the cross section for (off-resonant) Raman scattering is basically the derivative of the dielectric constant with respect to the amplitude of the vibrational distortion. I do not know what exactly is measured (you probably do), but this is what is calculated, and the dielectric tensor of a metal is infinite ... in any case, it is always a good idea to know what is measured (which I don't, in this case), and what is calculated (which you do not seem to do, in this case ...).<div><br></div><div>graphene may be another story, because the density of states at the fermi energy is zero ...</div><div><br></div><div>Stefano B</div><div><br></div><div><div><div>On Jun 15, 2010, at 2:56 PM, loc duong ding wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>I don't understand why Raman activity in this case is zero. In practical, metallic system also provide Raman peak (ex. Carbon nannotube). I try to calculate graphene (no gap) and I get the proper result. Can you give some more explanation or suggest me some reference about this topic?<br><br> I appreciate to your instructions. <br><br><blockquote type="cite">So, the the Raman activity should be <br></blockquote><blockquote type="cite">zero ...<br></blockquote><blockquote type="cite">SB<br></blockquote><br>On Jun 15, 2010, at 3:50 AM, loc duong ding <br><blockquote type="cite">wrote:<br></blockquote><br><blockquote type="cite">I calculate zigag nano ribbon with hydrogen terminated at the <br></blockquote><blockquote type="cite">edge. I checked DOS that showed no gap. <br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><blockquote type="cite">yes - SB<br></blockquote></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">On Jun 14, 2010, at <br></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">11:03 AM, loc duong ding <br></blockquote></blockquote></blockquote><blockquote type="cite">wrote:<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">what's the gap of the <br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">unperturbed <br></blockquote></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">system?<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">SB<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">Actually, <br></blockquote></blockquote><blockquote type="cite">this <br></blockquote><blockquote type="cite"><blockquote type="cite">is the firs time I calculate the Raman spectrum. I don't clear <br></blockquote></blockquote><blockquote type="cite">about the gap of <br></blockquote><blockquote type="cite"><blockquote type="cite">the unperturbed system? It means the electronic <br></blockquote></blockquote><blockquote type="cite">band gap?<br></blockquote><br><br> -----------------------------------------------<br>Loc Duong Dinh<br>Ms-Ph.D Student<br>Sungkyunkwan Advanced Institute of Nanotechnology,<br>Sungkyunkwan University,<br>Suwon, 440-746, Korea <br>Email: <a href="mailto:mambom1902@yahoo.com">mambom1902@yahoo.com</a>, <a href="mailto:ddloc@skku.edu">ddloc@skku.edu</a><br><br><br><br>_______________________________________________<br>Pw_forum mailing list<br><a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>http://www.democritos.it/mailman/listinfo/pw_forum<br></div></blockquote></div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; 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"><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">---</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">Stefano Baroni - SISSA</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">&</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">DEMOCRITOS National Simulation Center - Trieste</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><a href="http://stefano.baroni.me">http://stefano.baroni.me</a> [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; font-size: 12px; "><br style="font-size: 12px; "></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; font-size: 12px; "><span class="Apple-style-span" style="font-size: 14px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><br></span></font></div></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">Please, if possible, don't</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">send me MS Word or PowerPoint attachments</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">Why? See:</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "> </span></font><font class="Apple-style-span" color="#0023E9" size="3"><span class="Apple-style-span" style="font-size: 12px; "><a href="http://www.gnu.org/philosophy/no-word-attachments.html">http://www.gnu.org/philosophy/no-word-attachments.html</a></span></font></div><div><font class="Apple-style-span" color="#0023E9" size="3"><span class="Apple-style-span" style="font-size: 12px; "><br class="webkit-block-placeholder"></span></font></div></div></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"></span><br class="Apple-interchange-newline">
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