ABINIT Discussion Forums

Which parameter is added to the LO-TO split when calculating the phonon spectrum？

See, e.g. eq 61 in

http://iffwww.iff.kfa-juelich.de/~wortm ... l45/C2.pdf

There is a sum evaluated over the different born charges projected on the TO mode you want to renormalize. The change is non-analytical in the sense that it depends on which direction your q vector points when you take the limit q -> 0 (discontinuous at Gamma).

Hello. Thank you very much for your reply. I really count the ion system. I am repeating the literature to calculate the phonon spectrum of barium titanate. There is a split in the literature, I think it should be a parameter to split

I don't understand what you mean by parameter.

The formula cited calculates the value of the LO-TO phonon frequency split, and is calculated in anaddb for each q vector direction (q->0) given in the "second list of q2ph" (see the tutorials on response functions).

Thank you very much, I have solved my problem.