Zone center wavenumbers of tetragonal AGa₂X₄ (A = Cd, Zn; X = S, Se)

Abstract

A short-range force constant model (SRFCM) was applied to investigate the phonons in AGa 2 X 4 (A = Cd, Zn; X = S, Se) defect chalcopyrite compounds in the tetragonal phase. The calculation with six stretching and one bending force constants in the SRFCM agrees well with the observed Raman and infrared wavenumbers. In CdGa 2 X 4 , the nearest Ga -X interatomic force constants of its bonds were found to be stronger than the nearest Cd -X interatomic force constants, whereas in ZnGa 2 X 4 , the nearest Zn -X interatomic force constants of its bonds were found to be weaker than the nearest Zn -X interatomic force constants. The variation of interatomic force constants is discussed. The dominant force constants have nearly the same ratio when Se replaces S.