[Pw_forum] Symmetry problem in phonon

[mayank gupta]

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