[Pw_forum] finding symmetry

Paolo Giannozzi giannozz at nest.sns.it
Tue May 27 19:00:06 CEST 2003

On Friday 23 May 2003 16:37, ma Yanming wrote:
> [...] this problem is from that the fractional translation
> is incompatible with the FFT grid.
> Is this behavior of finding less symmetries harmful to the calculation
> without concerning the calculating time?

no, it is not. The system must converge to the solution with the
good symmetry, whether it is imposed or not.

> How to solve it if I have to fix the unit cell and ecutwfc?

you can specify in input a slightly enlarged (or reduced, at your risk) 
FFT grid that is commensurate with the fractional translation

Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050509412
Piazza dei Cavalieri 7      Fax:     +39/050509417, 050563513     
I-56126 Pisa, Italy         Office:  Lab. NEST, Via della Faggiola 19

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