<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Dear Miriam: you and others will forgive my ignorance, but I would need some further explanations. According to the usual theory, they both should be zero:````````````````````` the second is given by Born effective charges (that are zero in metals), the former by the derivative of the inverse macroscopic electric constant (which is also zero). How can a metal be Raman or IR active? Thanks - SB<div><br><div><div>On Dec 14, 2007, at 7:18 PM, Miriam Marques wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"> Dear ESPRESSO users,<br><br> I would like to know if it is possible to compute<br> Raman and Infrared intensities for a metallic system.<br><br> Thank you very much in advance,<br><br> Miriam.<br><br> Dr. Miriam Marques<br> Centre for Science at Extreme Conditions.<br> The University of Edinburgh.<br> e-mail: <a href="mailto:mmarques@staffmail.ed.ac.uk">mmarques@staffmail.ed.ac.uk</a><br><br><br>-- <br>The University of Edinburgh is a charitable body, registered in<br>Scotland, with registration number SC005336.<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></blockquote></div><br><div> <span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); 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