RAMAN-STUDY AND LATTICE-DYNAMICS CALCULATION OF THE MISFIT LAYER COMPOUND (PBS)(1.12)VS2

The UV-visible (340-800 nm) and Raman spectra (10-900 cm(-1)) obtained using various laser exciting radiation of a powder sample of the misf it compound (PbS)(1.12)VS2 were investigated, In agreement with x-ray data, vibrational assignments are proposed for most of the internal an d external modes of the 'PBS' and 'VS2' layered sublattices and they w ere extensively compared with those in the related titanium-containing compound in order to appreciate the interactions due to the 'PbS' don or part of the structure, Owing to the incommensurate structure of (Pb S)(1.12)VS2, new slightly resonance exhanced Raman signals are detecte d and they can be explained by the k = 0, +/- q selection rules (q* i s the modulation vector) as in a previous study of (SnS)(1.7)NbS2 and (PbS)(1.18)TiS2 compounds. These observations are again confirmed by l attice dynamics calculations which reproduce the essential features of the experimental data and allow one to estimate the strength of inter layer interactions.