<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Try to increase the number of k points and let us know what happens. If, as I guess, the zone-center acoustic modes soften, try to understand why, starting from the early literature on DFPT. A good starting point could be e.g., <meta charset="utf-8"><span class="Apple-style-span" style="color: rgb(50, 50, 50); -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; "><a href="http://link.aps.org/doi/10.1103/PhysRevB.33.7017">http://link.aps.org/doi/10.1103/PhysRevB.33.7017</a> and</span> <span class="Apple-style-span" style="color: rgb(50, 50, 50); -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; "><a href="http://link.aps.org/doi/10.1103/PhysRevLett.62.2853">http://link.aps.org/doi/10.1103/PhysRevLett.62.2853</a> .</span><div><font class="Apple-style-span" color="#323232"><span class="Apple-style-span" style="-webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px;">Hope this helps</span></font></div><div><font class="Apple-style-span" color="#323232"><span class="Apple-style-span" style="-webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px;">Stefano Baroni</span></font></div><div><font class="Apple-style-span" color="#323232"><span class="Apple-style-span" style="-webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px;"><br></span></font><div><div>On Jul 2, 2011, at 12:02 PM, mayank gupta wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>Thanks Sir for your response.<br><br>I am doing all these calculations for oxides. for example I have done<br>the phonon calculations for Cu2O and Ag2O system the details are as<br>follow<br><br>Ag2O ecutwfc 70 Ry. Mesh (8x8x8) zone ceneter acoustic<br>mode=1.6 THz (with PBE)<br>Cu2O ecutwfc 95 Ry. Mesh (8x8x8) zone centre acoustic mode =<br>1.33 THz (PW)<br><br>I have performed above calculation using tr2_ph=1.0e-14, but the<br>values are almost same. the ecutrho=20times of ecutwfc.<br><br><br>Mayank<br><br><br><blockquote type="cite">Dear Mayanka,<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">is this a polar material? If so, the violation of the ASR may be justified<br></blockquote><blockquote type="cite">by the use of too coarse a k-point mesh. Please, provide more details on the<br></blockquote><blockquote type="cite">system and the calculations you are doing.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">SB<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">On Jul 1, 2011, at 6:17 AM, mayank gupta wrote:<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><blockquote type="cite">Dear All<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">I have a query ragrdin phonon calculations at q=0. When I performed<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">the phonon caclualtion at q=0, we didn't get zero enrgy for acoustic<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">branches, however they can be set to zero by using acoustic/ crystal<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">sum rules. My question is if the zone center acoustic braches values<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">are too large (4 THz) even we have implemented very high convergence,<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">it is ok to apply ASR.<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">Thanks<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">--<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">Mayank<br></blockquote></blockquote><br><br>BHABHA ATOMIC RESEARCH CENTER<br>MUMBAI, INDIA<br>Office: 022-25595606<br>Home: 9920397437 / 9869834437<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-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: 0px; font-size: medium; "><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font-size: 14px; "><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-size: 14px; "><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-size: 14px; "><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-size: 14px; "><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-size: 14px; "><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><div><font class="Apple-style-span" color="#0023E9" size="3"><br></font></div></span><br class="Apple-interchange-newline">
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