You can make a calculation at a q point that has imaginary frequencies, verify if you get the same result or if it is an artifact of Fourier interpolation
P. On Tue, 2013-06-18 at 09:38 +0800, Wei-Bing Zhang wrote: > Dear all > > > Recently, I am trying to calculate the phonon dispersion of 2D > materials. I used 4x4x1 q-points in phonon calculation whereas a > 16x16x1 k-points for self-consistent electronic calculation. The > direct calculations indicate that all phonons frequencies are above > zero on the grid of q-vectors including the Gamma point. However, when > I transformed the dynamical matrices from G- to R-space and calculated > phonon dispersions using ?matdyn.x?, some negative frequencies appear > in acoustic mode ZA near Gamma point. Since I am really a new user > for phonon calculation, I am not sure what happened. The input and > output file are enclosed. Could you tell me what?s wrong with my > calculations? Any suggestions will be appreciated. > > > > Thanks and best regards > > > > Wei-Bing Zhang > > > > > ---------------------------------------------------------------------- > 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 > ---------------------------------------------------------------------- > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- Paolo Giannozzi, Dept. Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
