are you imposing acoustic sum rule ? this change slightly the frequencies . isn't strange that your frequencies are all negative (imaginary) ? is your system stable ? stefano
05/11/2011 01:20 PM, S. K. S. wrote: > Dear All, > > I find a bit strange results when using matdyn.x to perform the > interpolation in order > to get a complete phonon dispersion plot. > > In case of my system, at Gamma point, ph.x prints out two noticeably > distinguishable triply degenerate phonon modes of frequency values as > follows : > > -18.9595 -18.9595 -18.9595 -11.8835 -11.8835 -11.8835 > > However, after using "matdyn.x" the above phonons become like : > > -18.6356 -18.6356 -18.6356 -18.6096 -18.6096 -18.6096 > > This looks quite strange to me. As far as I understand, the phonon > interpolation should > not change the frequency values at Gamma point or any other > high-symmetry point > (suppose X in my case) which have been already computed by the > QE_phonon code. Interpolation means, it should only generate more > frequencies in between > Gamma and X point, not changing the frequency values in the exact > Gamma and X point, which have been already printed by the ph.x run. > > Looking forward to your comments. > > Thanking you and with my best regards, > > Saha S. K. > R&D Assistant, > JNCASR > Bangalore -560064 > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum
