[Pw_forum] negative frequency in high q-mesh

[Paolo Giannozzi]

On Thu, 2013-01-31 at 15:32 +0800, Wei-Bing Zhang wrote:

> Unfortunately, I can only get the reasonable phonon dispersion
> with q-mesh below 6x6x1

what makes you think that the results with denser q-mesh 
are unreasonable? Are you sure that silicene is mechanically
stable? if not, there can be phonons with negative (actually
imaginary) frequency

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