[Pw_forum] about phonon by grid
marcel at physik.tu-berlin.de
Tue Sep 18 15:02:59 CEST 2007
On Tue, 18 Sep 2007, Ezad Shojaee wrote:
> when i calculate the IFC's by a (2 2 2) grid, and also (3 3 3) the dispersion curve seems to be reasonable and also converging; but when i try (4 4 4) grid, it comes with a lot of huge negative figures! what may be the problem?
> Explore the seven wonders of the world
4 4 4 is not so big. I would think small changes will occur if you
What system do you calculate?
Are the acoustic frequencies negative, or other ones too. How did you
caluclate the dispersion, did you impose acoustic sum rule or similar?
Maybe your system is not well relaxed, e.g., you are in a local
energy minimum and not the global one?
Marcel Mohr Institut für Festkörperphysik, TU Berlin
marcel(at)physik.tu-berlin.de Sekr. PN 5-4
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