[Pw_forum] Sound velocity calculation

[lfhuang]

Dear P. B. Sorokin: 
> But when I try to evaluate the velocity I obtain the answer nearly in
> six time less then reported early: 2200 m/s and 3400 m/s vs. 12200
> m/s and 19500 m/s.
> I do some stupid mistake, but where? Does anybody has the experience
> in such calculations?
Where does your reference for the sound velocity come from? And there are 3 acoustic bands for graphene, one of which is the bending mode with a parabolic dispersion near gamma point. Have you pay attention to this band?
 
Best Wishes!
Yours Sincerely
L.F.Huang

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L.F.Huang(黄良锋) DFT and phonon physics
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Add: Research Laboratory for Computational Materials Sciences,
Instutue of Solid State Physics,the Chinese Academy of Sciences,
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Web: http://theory.issp.ac.cn (website of our theory group)
http://www.issp.ac.cn    (website of our institute)
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