Abstract:
It is shown that nonadiabatic corrections to the dispersion law of optical phonons in the region of small wave vectors in the case of branches, for which the vibration with a zero wave vector is not accompanied by the appearance of a dipole moment in the ionic lattice, are significant for all possible directions of the wave vector. If a dipole moment arises, nonadiabatic corrections reach a noticeable value only for the wave-vector directions that are almost perpendicular to the direction of the dipole moment.
Fulltext:
PDF file (148 kB)