[Pw_forum] about larger system's frequence calculation

[Paolo Giannozzi]

On Aug 1, 2009, at 5:59 , lidonglin556 wrote:

>   Did you calculate some larger system's frequence? [...]
> I want to calculate a larger system of 100 atoms' frequence
> and hope it quickly.

>

you mean: vibrational frequences? you can't calculate
vibrational frequencies for 100 atoms quickly. It takes
3*100 linear-response calculations per phonon wavevector,
each one costing as much as, and usually more than, the
corresponding self-consistent calculation. A 40-atom calculation
for 11 wavevectors took 10 days on a fast PC, many hours on
a parallel machine

Paolo
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Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222