[Pw_forum] phonon frenquecies convergences

[Paolo Giannozzi]

On Mon, 2012-01-09 at 10:11 +0000, hichem bouderba wrote:

> Suppose that one performs a convergence study for just one q-point
> (say Gamma for example), is it reasonable to expect that results will
> be reliable for other q-points ?

if you check convergence wrt cutoff, or wrt k-points in insulators, 
I would say it is reliable. Convergence wrt k-points may be very 
tricky in metals, though, due to the presence of Kohn anomalies.

> Does the last line mean :
> (a) Do not use it with non cubic symmetries.
> (b) One may use it, but results should be carefully checked for
> eventual problems. In this case, wath kind of problems one may expect.

no major problems, I think: the DOS close to Gamma may be inaccurate

P.

-- 
Paolo Giannozzi, IOM-Democritos and University of Udine, Italy