[Pw_forum] Mysterious Matdyn Messages - More

[Paolo Giannozzi]

On Fri, 2012-01-27 at 09:30 -0800, W2AGZ wrote:

> I found the portion of subroutine dyndiag you referred to, and it
> should have been obvious to me that a non-hermitian issue is present.
> This may be due to the fact that the system, polysulfur nitride, I’m
> studying is “quite” monoclinic, and the nq Monkhorst-Pack grid (2x2x2)
> I’ve used does not sufficiently reflect this low symmetry.

I don't think this is a problem. The opposite is a source of
problems: when you have a grid that doesn't reflect the
symmetry of your crystal

>   Is there a “rule of thumb” for setting the MP phonon grid for non-cubic systems? 

the longer the axis, the smaller the MP index, so that the
spacing along the three axis is approximately the same?

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