[Pw_forum] ecutrho in phonon calculations

[Paolo Giannozzi]

On Thu, 2012-04-12 at 16:07 -0400, YY wrote:

> But I find there is no simple convergence trend while increasing
> ecutrho.  When I use 35 Ry ecutwfc, and fix all the other parameters,
> the results are like this:
> 
>    ecutrho       f1(cm-1)      ....  f12(cm-1)
>    420            40.475                324.062
>    600           123.746               350.727
>    900           -251.876              306.721

unfortunately in at least some [ and I am afraid, in many ] cases,
a rather high cutoff is needed anyway to get decent phonons. If 
this happens, the advantage of using USPP becomes dubious, given 
their significant computational overhead wrt Norm-Conserving PPs. 
Which USPP did you use ?

P.

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