Crystal structure a cobalt molybdate type φx: NaCo2OH(H2O)(MoO4)2

Abstract

A cobalt molybdate with the formula NaCo2OH(H2O)(MoO4)2 was synthesized by hydrothermal reaction at 200°C in 3 days. The structure was determined from powder data by means of the EXPO direct methods program and refined with GSAS. The purple solid crystallizes in the monoclinic space group C2/m with a=9.3789(3), b=6.3330(1), c=7.6280(2) Å, and β=115.833(2)a. Octahedral cobalt atoms, centered at 1/4b and 3/4b, share edges to create endless chains running parallel to the b axis. The chains are connected through molybdenum tetrahedra, which share two vertices with consecutive octahedra in one chain and extend the third vertex to an adjacent chain; the fourth vertex protrudes into the interlayer space. This arrangement repeats itself indefinitely in the ab plane to create a layered structure.