Vibrational multiplet structure of internal optic modes in crystals

Abstract

Vibrational multiplet structure in Brillouin zone center internal optic modes can be classed as originating from site group effects, multiple site effects, and correlation field or factor group effects. In many systems where these may occur simultaneously, the separate contributions of each of these effects can be calculated in terms of a molecular dipole model. An example of site group/factor group splitting in orthorhombic KNO₃ is analyzed and discussed.