Figure : Crystallographic structure of Bi 0.852 V 0.148 O 1.648 (also known as β -Bi 46 V 8 O 89 ), shown along the [1 10] direction, as reported by Kuang et al. Bismuth atoms are shown in purple, oxygen atoms in red, and vanadium atoms (and VO 4 tetrahedral units) in brown. The monoclinic (space group C2/m) structure comprises a characteristic stacking of two layers containing VO 4 tetrahedra (Bi 14 V 4 O 31 ) and one bismuth oxide rock salt layer (Bi 18 O 27 ) containing only OBi 4 units. All VO 4 groups are isolated.