Far-infrared single-crystal study of potassium tetrabromoplatinate(II)

Abstract

It is shown from far-i.r. reflectance measurements on a single crystal of K₂[PtBr₄] that the internal modes ν₂(A_2u),-π(Pt–Br) and ν₇(E_u),δ(Pt–Br) are almost accidentally degenerate at 128 and 129 cm^–1 at 295 K and 129 and 133 cm^–1 at 38 K. The lattice modes are in the order E_u > A_2u > E_u. The principal values of the low-frequency dielectric constant are estimated to be 7.06 [ε(1)=ε(2)] and 4.20 [ε(3)].