Materials Data on NaCaSb2O7 by Materials Project
NaCaSb2O7 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Na is bonded to eight O atoms to form distorted NaO8 hexagonal bipyramids that share edges with two equivalent NaO8 hexagonal bipyramids, edges with four equivalent CaO8 hexagonal bipyramids, and edges with six SbO6 octahedra. There are a spread of Na–O bond distances ranging from 2.31–2.63 Å. Ca is bonded to eight O atoms to form distorted CaO8 hexagonal bipyramids that share edges with two equivalent CaO8 hexagonal bipyramids, edges with four equivalent NaO8 hexagonal bipyramids, and edges with six SbO6 octahedra. There are two shorter (2.23 Å) and six longer (2.58 Å) Ca–O bond lengths. There are two inequivalent Sb sites. In the first Sb site, Sb is bonded to six O atoms to form SbO6 octahedra that share corners with six SbO6 octahedra, edges with two equivalent CaO8 hexagonal bipyramids, and edges with four equivalent NaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 45–46°. All Sb–O bond lengths are 2.01 Å. In the second Sb site, Sb is bonded to six O atoms to form SbO6 octahedra that share corners with six SbO6 octahedra, edges with two equivalent NaO8 hexagonal bipyramids, and edges with four equivalent CaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 46–47°. There are four shorter (2.00 Å) and two longer (2.02 Å) Sb–O bond lengths. There are four inequivalent O sites. In the first O site, O is bonded to two equivalent Na and two equivalent Ca atoms to form ONa2Ca2 tetrahedra that share corners with sixteen ONa2Ca2 tetrahedra and edges with six ONaCaSb2 tetrahedra. In the second O site, O is bonded to one Na, one Ca, and two Sb atoms to form a mixture of distorted edge and corner-sharing ONaCaSb2 tetrahedra. In the third O site, O is bonded to two equivalent Na and two equivalent Sb atoms to form a mixture of distorted edge and corner-sharing ONa2Sb2 tetrahedra. In the fourth O site, O is bonded to two equivalent Ca and two equivalent Sb atoms to form a mixture of distorted edge and corner-sharing OCa2Sb2 tetrahedra.