title: Contribution of disulfide S2(2-) anions to the crystal and electronic structures in ternary sulfides, Ba12In4S19, Ba4M2S8 (M=Ga, In).
abstract: Three semiconducting ternary sulfides have been synthesized from the mixture of elements with about 20% excess of sulfur (to establish oxidant rich conditions) by solid-state reactions at high temperature. Ba(12)In(4)S(19) ≡ (Ba(2+))(12)(In(3+))(4)(S(2-))(17)(S(2))(2-), 1, crystallizes in the trigonal space group R ̅3 with a = 9.6182(5) Å, b = 9.6182(5) Å, c = 75.393(7) Å, and Z = 6, with a unique long period-stacking structure of a combination of monometallic InS(4) tetrahedra, linear dimeric In(2)S(7) tetrahedra, disulfide S(2)(2-) anions, and isolated sulfide S(2-) anions that is further enveloped by Ba(2+) cations. Ba(4)In(2)S(8) ≡ (Ba(2+))(4)(In(3+))(2)(S(2-))(6)(S(2))(2-), 2, crystallizes in the triclinic space group P ̅1̅ with a = 6.236(2) Å, b = 10.014(4) Å, c = 13.033(5) Å, α = 104.236(6)°, β = 90.412(4)°, γ = 91.052(6)°, and Z = 2. Ba(4)Ga(2)S(8) ≡ (Ba(2+))(4)(Ga(3+))(2)(S(2-))(6)(S(2))(2-), 3, crystallizes in the monoclinic P2(1)/c with a = 12.739(5) Å, b = 6.201(2) Å, c = 19.830(8) Å, β = 104.254(6)° and Z = 4. Compounds 2 and 3 represent the first one-dimensional (1D) chain structure in ternary Ba/M/S (M = In, Ga) systems. The optical band gaps of 1 and 3 are measured to be around 2.55 eV, which agrees with their yellow color and the calculation results. The CASTEP calculations also reveal that the disulfide S(2)(2-) anions in 1-3 contribute mainly to the bottom of the conduction bands and the top of valence bands, and thus determine the band gaps.
authors: Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China.
authors: Ji-Wei
authors: JW
authors: Liu
authors: Peng
authors: P
authors: Wang
authors: Ling
authors: L
authors: Chen