Raman spectroscopy in AB2X4 pseudoternary layered compounds

We have synthesized several pseudoternary layered compounds by cation or anion cross substitution in ternary AB₂X₄ compounds. Here we report on the low frequency Raman spectra obtained from Zn_xCd_1-xIn₂S₄, Zn(In_xGa_1-x)₂S₄ and ZnIn₂(S_xSe_1-x)₄ single crystals. Within these systems we have identified five compositionally or dynamically different phases. Each of these phases may be characterized by its peculiar low frequency Raman spectrum which is connected to the dynamics of the layers in the unit cell. Abrupt structural/dynamical changes are observed as a function of composition between different phases. Within each phase compositional changes cause only smooth and small spectral variations.