[Pw_forum] Separating Raman modes

[Paolo Giannozzi]

Zubaer Hossain wrote:

> How about decomposing eigenstates into that for the individual atoms and 
> summing them for each species, since the phonon frequencies are computed 
> already, and the eigenmodes for each frequency are known. By analyzing 
> these quantities graphically for each species, optical frequencies of 
> the main three modes could be detected, I think.

years ago we did something similar:
    "Phonon Dispersions in Ga(x)Al(1-x)As Alloys", PRL 65, 84 (1990).
Alloy modes were projected over crystal modes. In that particular
case the "mass approximation" was giving an accurate and convenient
way to calculate the dynamical matrix in relatively large supercells

Paolo
-- 
Paolo Giannozzi, Democritos and University of Udine, Italy