[Pw_forum] Phonon LO-TO splitting in semiconductor with smearing

[Hans Lind]

Thanks for the response, but not sure how useful it is.
To get the fermi smearing I set the following input lines

occupations='smearing'
smearing='fermi-dirac'
degauss=0.01 (fermi temperature in Ry, about 1500K, I want to set it higher
also)

The smearing would ensure that states are no longer either fully occupied
or empty. And I am not sure either of what you mean by commenting out check
on LO-TO splitting and smearing. As I have used it before, as long as I
don't specify smearing I get the LO-TO splitting automatically.

2012/4/13 Paolo Giannozzi <giannozz at democritos.it>

>
> On Apr 13, 2012, at 11:26 , Hans Lind wrote:
>
>  I am trying to do phonon calculations on AlN at non-zero fermi temperature
>> to get forces recalculated for higher temperatures. But since I need to
>> use
>> smearing for that the code won't do LO-TO splitting as is needed in a
>> semiconductor.
>>
>
> if you comment out the check on LO-TO splitting and smearing, and if all
> states are
> either fully occupied or empty, you should still get a LO-TO splitting.
> Not sure what
> it means, though. The phonon formalism is supposed to work at zero
> temperature.
> Not sure what it takes to extend the formalism to cover finite-temperature
> effects.
>
> P.
> ---
> Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>
>
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