Materials Data on MgCu2AsO7 by Materials Project
MgCu2AsO7 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Mg is bonded to six O atoms to form MgO6 octahedra that share corners with three equivalent AsO4 tetrahedra and edges with four CuO5 square pyramids. There are a spread of Mg–O bond distances ranging from 2.06–2.18 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded to five O atoms to form distorted CuO5 square pyramids that share a cornercorner with one CuO5 square pyramid, corners with three equivalent AsO4 tetrahedra, edges with two equivalent MgO6 octahedra, and an edgeedge with one CuO5 square pyramid. There are a spread of Cu–O bond distances ranging from 1.85–2.47 Å. In the second Cu site, Cu is bonded to five O atoms to form distorted CuO5 square pyramids that share a cornercorner with one CuO5 square pyramid, corners with two equivalent AsO4 tetrahedra, edges with two equivalent MgO6 octahedra, and an edgeedge with one CuO5 square pyramid. There are a spread of Cu–O bond distances ranging from 1.82–2.43 Å. As is bonded to four O atoms to form AsO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with five CuO5 square pyramids. The corner-sharing octahedra tilt angles range from 45–46°. There are a spread of As–O bond distances ranging from 1.68–1.75 Å. There are seven inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to two Cu and one As atom. In the second O site, O is bonded in a 3-coordinate geometry to one Mg, one Cu, and one As atom. In the third O site, O is bonded in a trigonal non-coplanar geometry to one Mg and two Cu atoms. In the fourth O site, O is bonded in a distorted trigonal planar geometry to one Mg, one Cu, and one As atom. In the fifth O site, O is bonded in a trigonal non-coplanar geometry to one Mg and two Cu atoms. In the sixth O site, O is bonded in a water-like geometry to one Mg and one Cu atom. In the seventh O site, O is bonded in a distorted trigonal planar geometry to one Mg, one Cu, and one As atom.