DOE OSTI2020
Mo3Cd2O8 is Marcasite-derived structured and crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Mo4+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two equivalent CdO6 octahedra, corners with three equivalent CdO4 tetrahedra, an edgeedge with one CdO6 octahedra, and edges with four equivalent MoO6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are a spread of Mo–O bond distances ranging from 2.02–2.18 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to four O2- atoms to form CdO4 tetrahedra that share corners with three equivalent CdO6 octahedra and corners with nine equivalent MoO6 octahedra. The corner-sharing octahedra tilt angles range from 60–68°. There are one shorter (2.21 Å) and three longer (2.22 Å) Cd–O bond lengths. In the second Cd2+ site, Cd2+ is bonded to six O2- atoms to form CdO6 octahedra that share corners with six equivalent MoO6 octahedra, corners with three equivalent CdO4 tetrahedra, and edges with three equivalent MoO6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are three shorter (2.30 Å) and three longer (2.43 Å) Cd–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Mo4+ and two Cd2+ atoms to form a mixture of edge and corner-sharing OCd2Mo2 tetrahedra. In the second O2- site, O2- is bonded in a trigonal planar geometry to two equivalent Mo4+ and one Cd2+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Mo4+ atoms. In the fourth O2- site, O2- is bonded to three equivalent Mo4+ and one Cd2+ atom to form a mixture of distorted edge and corner-sharing OCdMo3 tetrahedra.