Materials Data on Mg2NiH4 by Materials Project

Abstract

Mg2NiH4 crystallizes in the orthorhombic Pccn space group. The structure is three-dimensional. there are three inequivalent Mg sites. In the first Mg site, Mg is bonded in a 7-coordinate geometry to seven H atoms. There are a spread of Mg–H bond distances ranging from 2.06–2.32 Å. In the second Mg site, Mg is bonded to six H atoms to form distorted MgH6 octahedra that share corners with four equivalent MgH6 octahedra, corners with two equivalent NiH4 tetrahedra, edges with two equivalent MgH6 octahedra, and edges with two equivalent NiH4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–84°. There are a spread of Mg–H bond distances ranging from 2.24–2.33 Å. In the third Mg site, Mg is bonded to six H atoms to form distorted MgH6 octahedra that share corners with four equivalent MgH6 octahedra, corners with two equivalent NiH4 tetrahedra, edges with two equivalent MgH6 octahedra, and edges with two equivalent NiH4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–84°. There are a spread of Mg–H bond distances ranging from 2.04–2.22 Å. Ni is bonded to four H atoms to form NiH4 tetrahedra that share corners with two MgH6 octahedra and edges with two MgH6 octahedra. The corner-sharing octahedra tilt angles range from 73–92°. There are a spread of Ni–H bond distances ranging from 1.55–1.57 Å. There are four inequivalent H sites. In the first H site, H is bonded in a distorted rectangular see-saw-like geometry to three Mg and one Ni atom. In the second H site, H is bonded in a distorted see-saw-like geometry to three Mg and one Ni atom. In the third H site, H is bonded to four Mg and one Ni atom to form a mixture of distorted edge and corner-sharing HMg4Ni square pyramids. In the fourth H site, H is bonded in a distorted see-saw-like geometry to three equivalent Mg and one Ni atom.