RAMAN-SCATTERING IN DEFECTIVE AIIB2IIIX4VI COMPOUNDS AND ALLOYS

We have synthesized and characterized a variety of defective A(II)B2(I II)X4VI compounds and alloys, many of which display a layered structur e. Here we review and update Raman scattering results on both tetragon al and layered compounds. As to tetragonal compounds we check a simple bond stretching dynamical model, whereas for the layered structures w e propose a phenomenological picture of the vibrational dynamics based on the intrinsic high degree of disorder.