Raman Spectra of (NH₄)₂BeF₄

Abstract

Raman spectra of (NH₄)₂BeF₄ in the frequency range from 0 to 200 cm⁻¹ were measured from room temperature to the liquid nitrogen temperature, including the phase transition points T₁ (183 K) and T₂ (177 K). No soft-mode was observed in this temperature range. There are several lines belonging to the A₁ and B₂ irreducible representations which were observed only in the phase III.