Hi
I have performed phonon calculation for silver oxide with mesh size 8x8x8 and ecut off is 70 Ry erhocut=1050 Ry. I have tested the total energy convergence. We have used the pseudopotetial generated by using PBE . After SCF calculation we performed phonon calculation at different pressure with 2x2x2 q point using default cutoff parameters and calculate the gruneisen parameters. The calculated Gruneisen parameter and thermal expansion are in agreement with our previous calculation using potential model lattice dynamics as well as with experimental results. Again I have performed the same calculation with 4x4x4 q point mesh I find the entirely different result. my main concern is around q=0 because around that I found the significant change in phonon frequency. I have used matdyn.x to generate phonon frequency at intermediate point. Further in acoustic sum rule if I used asr=simple I am getting the negative frequency while asr=crystal I didn't get any negative phonon frequency. So I am confused which sum rule should use and how much q point I have to calculate. Kindly suggest me . Thanks A lot M K gupta
