Dear All I have done phonon calculation of a BCT system. I have chosen 2x2x2 q mesh for phonon calculation. While in real space force constant calculation (q2r.x) I am getting the waring and it says " fft-check warning: sum of imaginary terms =10-6". i ignored it and calculate the phonon frequencies. From symmetry at zone boundary along 001 all the phonon frequencies are doubly degenerate which is experimentally observed but i didn't get the degeneracy. the frequencies at 001 are differ by about 1-5 meV. kindly advice.
Thanks Mayank Research student BARC mumbai