A combined time-of-flight powder neutron and powder X-ray diffraction study of ternary chromium sulfides, VxCr3 –xS4(0⩽x⩽1.0)

Abstract

A combination of time-of-flight powder neutron diffraction and powder X-ray diffraction has been used to investigate the distribution of vanadium and chromium cations between two crystallographic sites in the series of ternary sulfides VxCr3 –xS4(0⩽x⩽1.0). These materials adopt the Cr3S4 structure (space group I2/m: a≈ 5.9, b≈ 3.4, c≈ 11.2 A; β≈ 91.4°) over the entire composition range. However, a marked change in the distribution of cations takes place in a region of composition in which anomalies have previously been observed in plots of cell parameters as a function of composition. Above x≈ 0.4, vanadium is almost equally apportioned between sites in a fully occupied cation layer and sites in an ordered vacancy layer, whereas at a composition V 0.2Cr2.8S4, vanadium preferentially occupies sites in the ordered vacancy layer.