[Pw_forum] BEC from DFPT

[Paolo Giannozzi]

On Feb 4, 2012, at 9:51 , 程迎春 wrote:

> If the system is insulator, WHY it must be treated as metallic?
> Would you please tell us the REASON?

because it is the only way to guarantee a smooth and safe
convergence to the ground state in a spin-polarized system,
if you do not want to constrain the final magnetization.

> I think you can try occupations='fixed' to get the Born effective
> charge for your system.

Not sure: the scf code may complain. It is one of the many
checks that are there to prevent a bad usage of the code.

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