The Ba10S(VO3S)6 Oxysulfide: One-Dimensional Structure and Mixed Anion Chemical Bonding

The new oxysulfide Ba 10 V 6 S 7 O 18 , which can be written as Ba 10 S(VO 3 S) 6 , was prepared by solid state reaction. It crystallizes in noncentrosymmetric space group P6 3 with the following unit cell parameters: a = 18.3018(2) Å and c = 8.6525(2) Å ( R 1 = 3.21%). This original phase exhibits (VO 3 S) units separated by Ba 2+ cations; the latter delimit one-dimensional (1D) hexagonal-like cavities filled by disordered sulfur S 2- anions and arranged into two kinds of sulfur-deficient 1D channels. Density functional theory calculations were employed to gain insights into the chemical bonding and parameters that determine the structure, particularly the V-O versus V-S bonding inside the mixed anion VO 3 S tetrahedra, and the contribution of the S 2- of the cavities. The title compound can be decomposed with three components mainly interacting by ionic bonds as follows, Ba 10 V 6 S 7 O 18 → [Ba 10 ] 20+ [S] 2- [(VO 3 S) 6 ] 18- ; this description may pave the way for the design of other phases related to this system with adjusted band gap features. In particular, the effect of the V(O,S) 4 :Ba ratio is discussed to emphasize the presence of the [S] 2- component, in comparison with related structures such as Ba 6 V 4 O 5 S 11 [Ba 6 (VO 2 S 2 ) 2 (VS 3 O)(VS 4 )], as it contributes strongly just below the Fermi level with subsequent alteration of the band gap.