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
