Raman Spectra in Molecular Solids II. Low Frequency Raman Spectroscopy as a Means to Study Phase Changes: More about the “Anomalous” γ-Phase of p-Dichlorobenzene

Abstract

Abstract The temperature dependence of the Raman low frequency spectra of the three solid polymorphic phases of p-dichlorobenzene has allowed us to prove that the so-called “anomalous” γ-phase is, in fact, the actual stable low temperature modification (below 279 K): we have shown that the transformation (α, γ) is reversible at atmospheric pressure. Our results and previous ones obtained under pressure by others lead us to deduce the existence of a triple point between the three solid phases of p-dichlorobenzene around room temperature and at pressures of the order of 500 bars.