Lattice dynamic investigation of Raman and infrared wavenumbers at the zone center of orthorhombic RFeO₃ (R = Tb, Dy, Ho, Er, Tm) perovskites

A short‐range force constant model was applied for the first time to investigate the phonons in RFeO 3 ( R = Tb , Dy, Ho, Er, Tm) perovskites in the orthorhombic phase. The calculations with the 12 stretching and three bending force constants provide good agreement for the observed Raman and infrared wavenumbers. The infrared wavenumbers were assigned for the first time. The variation of the force constants on going from Tb to Tm is discussed . The effect of changing the R ion from Tb to Tm in the Raman modes of RFeO 3 is also discussed.