[Pw_forum] test case with structure relaxation

[Paolo Giannozzi]

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.
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Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222