[Pw_forum] Raman intensity with or without ASR

[Paolo Giannozzi]

On Mon, 2015-02-02 at 09:55 +0100, Antoine JAY wrote:

> I have calculated a lot of Raman Spectra with QE which give very accurated
> results.

good to know

> But when I try to calculate Raman intensities with the eigenvectors
> obtained after ASR (crystals) results aren't that accurate. The ASR do not
> change my Raman frequencies, give 0 acoustic frequencies and change a bit
> eigenvectors as expected.

this doesn't sound right to me: why should Raman intensities change a
lot if eigenvectors don't? By the way, try asr='simple' before trying
other more sophisticated forms of ASR.

Paolo

> Question: Why do I have to take eigenvectors which are calculated BEFORE
> the ASR in the calcul of the intensity ?
> (Equ.2 in Lazzeri, Mauri, PRL 90036401-1(2003))
> 
> Thanks a lot
> 
> Antoine JAY
> Doctorant (PhD student)
> Laboratoire des Solides Irradiés
> 
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-- 
 Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
 Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
 Phone +39-0432-558216, fax +39-0432-558222