title: Ba5Ga4Se10: a new selenidogallate containing the novel [Ga4Se10](10-) anionic cluster with Ga in a mixed-valence state.
abstract: The new compound Ba(5)Ga(4)Se(10) has been synthesized for the first time. It crystallizes in the tetragonal space group I4/mcm with a = 8.752(2) Å, c = 13.971(9) Å, and Z = 2. The structure contains discrete [Ga(4)Se(10)](10-) anions and charge-compensating Ba(2+) cations. The novel highly anionic [Ga(4)Se(10)](10-) cluster is composed of two Ga(Se)(4) tetrahedra and two Ga(Ga)(Se)(3) tetrahedra with Ga in the 2+/3+ valence states. It also exhibits an unusually long Ga-Se distance of 2.705(2) Å, which has only been observed under high pressure conditions before. A band gap of 2.20(2) eV was deduced from the UV/vis diffuse reflectance spectrum.
authors.affiliation: Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, PR China.
authors.forename: Wenlong
authors.initials: W
authors.lastname: Yin
authors.forename: Dajiang
authors.initials: D
authors.lastname: Mei
authors.forename: Kai
authors.initials: K
authors.lastname: Feng
authors.forename: Jiyong
authors.initials: J
authors.lastname: Yao
authors.forename: Peizhen
authors.initials: P
authors.lastname: Fu
authors.forename: Yicheng
authors.initials: Y
authors.lastname: Wu