Materials Data on MgCuAs by Materials Project

Abstract

MgCuAs crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to five As3- atoms to form distorted MgAs5 square pyramids that share corners with eight MgAs5 square pyramids, corners with eight CuAs4 tetrahedra, edges with six MgAs5 square pyramids, and edges with six CuAs4 tetrahedra. There are a spread of Mg–As bond distances ranging from 2.68–2.88 Å. In the second Mg2+ site, Mg2+ is bonded to five As3- atoms to form distorted MgAs5 square pyramids that share corners with four equivalent MgAs5 square pyramids, corners with twelve CuAs4 tetrahedra, edges with eight MgAs5 square pyramids, and edges with four CuAs4 tetrahedra. There are a spread of Mg–As bond distances ranging from 2.69–2.85 Å. There are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to four As3- atoms to form CuAs4 tetrahedra that share corners with twelve MgAs5 square pyramids, corners with four CuAs4 tetrahedra, edges with four MgAs5 square pyramids, and edges with four CuAs4 tetrahedra. There are one shorter (2.55 Å) and three longer (2.57 Å) Cu–As bond lengths. In the second Cu1+ site, Cu1+ is bonded to four As3- atoms to form CuAs4 tetrahedra that share corners with eight MgAs5 square pyramids, corners with eight CuAs4 tetrahedra, edges with six MgAs5 square pyramids, and edges with two equivalent CuAs4 tetrahedra. There are one shorter (2.52 Å) and three longer (2.56 Å) Cu–As bond lengths. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded in a 9-coordinate geometry to five Mg2+ and four Cu1+ atoms. In the second As3- site, As3- is bonded in a 9-coordinate geometry to five Mg2+ and four Cu1+ atoms.