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Professor Paulo,<div><br></div><div>thanks for your reply. Will do that.</div><div><br></div><div>Elie<br><br><div><div id="SkyDrivePlaceholder"></div>&gt; From: giannozz@democritos.it<br>&gt; Date: Fri, 24 Aug 2012 12:06:56 +0200<br>&gt; To: pw_forum@pwscf.org<br>&gt; Subject: Re: [Pw_forum] Negative frequencies at really low threshold        convergence<br>&gt; <br>&gt; <br>&gt; On Aug 23, 2012, at 20:46 , Elie M wrote:<br>&gt; <br>&gt; &gt;  I still get that the three first values of the frequencies are  <br>&gt; &gt; negative.<br>&gt; &gt; Does this confirm the instability of the system?<br>&gt; <br>&gt; likely, but you should first of all verify the effect of applying the<br>&gt; Acoustic Sum Rule.<br>&gt; <br>&gt; P.<br>&gt; ---<br>&gt; Paolo Giannozzi, Dept of Chemistry&amp;Physics&amp;Environment,<br>&gt; Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>&gt; Phone +39-0432-558216, fax +39-0432-558222<br>&gt; <br>&gt; <br>&gt; <br>&gt; <br>&gt; _______________________________________________<br>&gt; Pw_forum mailing list<br>&gt; Pw_forum@pwscf.org<br>&gt; http://www.democritos.it/mailman/listinfo/pw_forum<br></div></div>                                               </div></body>
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