Single Crystal X‐ray Structure of Cu3TaSe4 and a Comparative Study of Cu3MX4 (M = V, Nb, Ta; X = S, Se, Te)

Single crystals of Cu3TaSe4 were obtained by chemical vapor transport with iodine as transport agent. Cu3TaSe4 crystallizes in the sulvanite structure type with space group P3m and a = 5.6613(3) A at room temperature. Structure refinements against single-crystal X-ray diffraction data result in a Cu–Se distance slightly longer than the Ta–Se distance, whereas previous Rietveld refinements obtained a Cu–Se distance shorter than the Ta–Se distance [G. E. Delgado et al., J. Alloys Comp. 2007, 439, 346]. The structural variations of sulvanite type compounds Cu3MX4 (M = V, Nb, Ta; X = S, Se, Te) are discussed in view of small distortions of CuX4 and MX4 tetrahedra and the atomic valences.