[Pw_forum] further: born charges in rhombohedral unit cell.

[Stefano de Gironcoli]

On 04/08/2011 01:35 PM, sonu kumar wrote:
>   Respected Prof. Stefano de Gironcoli and QE users,
>
>> Are the symmetry operations determined in the two systems the same ?
> Yes.
>
>> because there is a symmetry reason.
>> like a mirror plane or something ...
>   Na(H)  and F have  D3d , C3v  site sym resp.
so, i guess, Na(H) should have diagonal Z* while F could have off 
diagonal one and could be non-symmetric ...

stefano

>> If your symmetry allows the born effective charge to be non zero they
>> will, much or little depending on the details of the system.
> NaHF2 is mainly ionic than CuAlO2, so one may  expect to have differences
> in born-effective charges.
>
> Thank you very much.
>
> with regards,
> Sonu
> IITD
>
>
>
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