On Jan 17, 2011, at 14:06 , Martin Andersson wrote: > I am looking into the effects of empirical dispersion, and as far as I > can see from the phonon output file, the effect from dispersion isn't > included when the frequencies are calculated using ph.x. Is there a > way > to use finite differences in the QE suite as opposed to perturbation > theory in order to get frequencies with empirical dispersion included?
there is for sure more than one way, but none currently implemented and ready to use, AFAIK. Once upon a time there used to be a frozen-phonon code, but nobody was maintaining it so it has been removed. In the Gamma/ subdirectory there is a piece of code that evaluates Raman coefficients using finite differences on the dielectic tensors. It was written for testing purposes several years ago and could be easily adapted to frozen-phonon calculations, but it will need some work. 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
