Dear Paolo, Denser k-point grid still yielded a converged ratio of 1.427 which is far from the expected 1.414 but thanks for the advice.
Regards, Wei On Wed, Mar 28, 2012 at 3:01 PM, Paolo Giannozzi <giannozz at democritos.it>wrote: > > On Mar 28, 2012, at 15:25 , Wei Lai wrote: > > I created a virtual tetragonal MgO cell with c/a ratio as 1.4. >> I was expecting this ratio will become close to 1.4142 (cubic) >> after relaxation. >> > > > your k-point grid is not symmetric and produces a small > symmetry breaking. A denser grid yields a more symmetric > final structure > > P. > --- > Paolo Giannozzi, Dept of Chemistry&Physics&Environment, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120329/2f4f1dce/attachment.htm
