[Pw_forum] Optical phonon convergence at Gamma-point

[Sophia Nishad]

Thanks, Paolo. I have little confusion about your comment though.

Earlier I had used norm-conserving PP in supercell calculations as well;
that produced converged frequency of  518.2 for Si. So, is it possible
that linear response calculations might not give better results compared
to supercell calculations (which is very expensive). The result could be
sensitive to the assumptions of linear response theory as well??

Thanks,
Sophia


On Mon, May 25, 2009 at 1:26 AM, Paolo Giannozzi <giannozz at democritos.it>wrote:

>
> On May 24, 2009, at 23:04 , Sophia Nishad wrote:
>
> > it is still off from the experiemntal value by ~8cm-1.
>
> both pseudopotentials and approximations to the exchange-correlation
> functional introduce intrinsic errors. It is quite hard to get any
> better
> results than those you get.
>
> Paolo
> ---
> Paolo Giannozzi, Democritos and University of Udine, Italy
>
>
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-- 
Sophia
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