[Pw_forum] apout phonon calculation

[Nicola Marzari]

Eric Abel wrote:
> Hi Ezad,
> 
> I performed a phonon calculation first using just a single k-point, then 
> I tried using a 2x2x2 grid, and compared these to eachother, then to 
> experiment, and found that 2x2x2 went a long way to describing the 
> system.  If you play around with the Al example (example 2), you find 
> that actually 2x2x2 already does a good job at producing the correct al 
> phonon dispersion curves and DOS.  I realize that the phonon 
> calculations are lengthy, but if it were easy, everybody would be doing 
> it, right?
> 
> Eric


Dear Eric,

some caveats. 2x2x2 is a very very coarse sampling for a system
with 1 atom per unit cell (bulk fcc Al). By using a large smearing,
and thanks to the fact that Al is very close to a free-electron gas,
you'll probably get decent results, but this is an exception, rather
than the rule.

nicola


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