Compositional disordering and some structural and optical parameters of Cu6P(S1−xSex)5Br mixed crystals

A series of Cu6P(S1−xSex)5Br solid solutions was studied at room temperature by X-ray diffraction and optical absorption measurements in the whole compositional range (0≤x≤1). The optical pseudogap, the absorption edge energy width, the cubic lattice parameter and calculated density of these mixed crystals were all found to change non-linearly with the composition x. These non-linear compositional dependencies were attributed to the effect of compositional disordering on the energy position and shape of exponential fundamental optical absorption edge in Cu6P(S1−xSex)5Br.