Dear Abolore Musari: In my opinion, lots of paper ran DFPT at 4x4x4 q-mesh. Sometimes (not often), 3x3x3 q-mesh may also provide reasonable results. The easiest way may be similar as k-mesh test, you can gradually increase the q-mesh from 2x2x2 to NxNxN until the frequencies converged (the threshold can be defined by yourself).
-- GAO Zhe CMC Lab, Materials Science & Engineering Department, Seoul National University, South Korea At 2012-08-12 12:47:12,"Abolore Musari" <abmus007 at gmail.com> wrote: >Dear sir. >Sir l just want to ask how do l know the proper nq1 nq2 nq3 to use in >my phonon calculation after my scf calculation. >Am sorry l ask this type of question l will be so happy if u can kindly explain >thanks >Musari. A.A >UNAAB Nigeria >_______________________________________________ >Pw_forum mailing list >Pw_forum at pwscf.org >http://www.democritos.it/mailman/listinfo/pw_forum -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120812/47d22f3d/attachment.htm