I found that optical branches are not continuous at gamma point (See figure below). I guess this is becasue the wrong LO-TO spiliting relation I got. How can I check it?
It is definitely because of LO-TO splitting, if it is wrong or not, well you can check how it converges with k-points. Dielectric constants and effective charges can be VERY slow to converge with k-points. Just repeat the phonon calculation at Gamma, no need to redo all the grid each time.
Or if you think the should be no LO-TO splitting at all (typically because of doping), just edit the first dyn matrix file (the one at gamma, i.e. dyn1) and remove all the section about epsilon and zeu, from
"Dielectric Tensor:" included, down to "Diagonalizing the dynamical matrix" excluded. hth -- Lorenzo Paulatto - Paris _______________________________________________ users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
