The reaction of Cu and V in a Rb2S5 melt yields black crystals of rubidium
dicopper vanadium tetrasulfide, RbCu2VS4. The structure is comprised of [Cu
2VS4](-) layers within the (010) plane which are separated by Rb+ cations.
The layers consist of a network of edge- and corner-sharing [VS4] and [CuS4
] tetrahedra parallel to (010). The optical band gap was determined as 1.45
eV.