Dear all, I am calculating the phonon modes at Gamma=0 for a 42 Carbon atom supercell. If N=42 then one has 3N= 3*42 modes= 128 modes. Just to confirm: (1) Are all the modes vibrational? (2) Are any modes missing from the calculation like optical or accoustical modes? (3) i did the calculation and got two of the modes negative which means either threshold is high or the ecutwav must be at least eight times ecutrho. Is a threshold of 10^(-15) still too high for such a system?
Thanks ElieUniversity of NottinghamNG7 2RDUK -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120514/3f5a2b63/attachment.htm
