Dear Prof. Giannozzi Thanks very much for your quick reply. The "unreasonable" just means there are few negative frequencies in acoustic phonon. Based on the published results about silicene (Phys. Rev. Lett. 102, 236804 (2009)), the silicene should be stable. On the other hand, as shown in the phonon spectrum of q-mesh (9, 9, 1) enclosed in the last message, the negative frequencies are only found in Gamma-K and M-Gamma region. So it seems to be induced some insufficient convergence or wrong setting of some parameters. However, I can?t get rid of it.
Wei-Bing On 31 January 2013 17:03, Paolo Giannozzi <giannozz at democritos.it> wrote: > 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 > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- ---------------------------------------------------------------------- Dr. Wei-Bing Zhang School of Physics and Electronic Sciences Changsha University of Science and Technology, Changsha, People?s Republic of China Phone : +86 186 73108538 E-mail: zwb256 at hotmail.com, weibingzhangavh at gmail.com ----------------------------------------------------------------------
