Frequency Shifts Calculated at High Pressures (ε–Ϛ Transition) in Solid Oxygen

Abstract

The pressure dependences of the Raman and infrared frequencies are predicted using a relation derived from the Vinet equation of state, which uses the mode Grüneisen parameter (γ_T) for the ε–Ϛ transition in solid oxygen. For this calculation, the observed data for V–P and ν–P are taken from the literature. The Grüneisen parameter of the Raman vibron calculated by us increases with increasing pressure because the observed Raman frequencies of this vibron increase. For the infrared modes, γ_T exhibits a nearly symmetrical profile (ν_FIR) and λ-type behaviour (ν_MIR) for the δ–ε transition (in the ε phase) in solid oxygen. Our calculated frequencies for the Raman and infrared modes agree with the observed data, which indicates that the modified ν–P relation can be used to predict frequencies close to phase transitions in various molecular crystals.