Dear Mayank!<br> There is no need to use this much high cutoff. First of all see proper convergence with k-points grids. Then "conv_thr" should be less than 10^-12. Before doing phonon calculation do vc-relax with high accuracy. And if you get very small negative value then you can ignore it..<br>
<br><br><div class="gmail_quote">On Wed, May 11, 2011 at 3:18 PM, mayank gupta <span dir="ltr"><<a href="mailto:mayankaditya@gmail.com">mayankaditya@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi Dear User's<br>
<br>
<br>
I am trying to calculate the phonon frequency of SrFeO compund, but I<br>
got negative frequancies at gamma also at other Q points, while I have<br>
chossen very high cutoff (ecut=100Ry and ecut_rho=1000), while<br>
experimentally the structure is stable at room temperature even up to<br>
very low temperature. what could be the possible reason for such<br>
negative frequecies.<br>
<br>
--<br>
Mayank<br>
<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Regards,<br>MOHNISH,<br>-----------------------------------------------------------------<br>Mohnish Pandey<br>Y6927262,5th Year dual degree student,<br>Department of Chemical Engineering,<br>
IIT KANPUR, UP, INDIA<br>-----------------------------------------------------------------<br>