PHONONS IN RED HGI2

A critical analysis of existing experimental and theoretical informati on on the lattice dynamics of the layered crystal alpha-HgI2 is perfor med. It is shown that a satisfactory understanding of the character of the interatomic interaction and characteristic features of the phonon spectrum of this material can be obtained in a simple phenomenologica l model with eight parameters, assuming that E-g/B-1g degeneracy of th e 29 cm(-1) Raman line is of a two-phonon nature. (C) 1998 American In stitute of Physics. [S1063-7834(98)03103-7].