MgH3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. Mg(1) is bonded in a body-centered cubic geometry to six equivalent H(1) and eight equivalent H(2) atoms. There are two inequivalent H sites. In the first H site, H(1) is bonded to six equivalent Mg(1) atoms to form HMg6 octahedra that share corners with six equivalent H(1)Mg6 octahedra, corners with twenty-four equivalent H(2)Mg4 tetrahedra, edges with twelve equivalent H(1)Mg6 octahedra, and faces with eight equivalent H(2)Mg4 tetrahedra. The corner-sharing octahedra are not tilted. In the second H site, H(2) is bonded to four equivalent Mg(1) atoms to form HMg4 tetrahedra that share corners with twelve equivalent H(1)Mg6 octahedra, corners with sixteen equivalent H(2)Mg4 tetrahedra, edges with six equivalent H(2)Mg4 tetrahedra, and faces with four equivalent H(1)Mg6 octahedra. The corner-sharing octahedral tilt angles are 55°.
MgH3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. Mg(1) is bonded in a body-centered cubic geometry to six equivalent H(1) and eight equivalent H(2) atoms. All Mg(1)-H(1) bond lengths are 2.35 Å. All Mg(1)-H(2) bond lengths are 2.04 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded to six equivalent Mg(1) atoms to form HMg6 octahedra that share corners with six equivalent H(1)Mg6 octahedra, corners with twenty-four equivalent H(2)Mg4 tetrahedra, edges with twelve equivalent H(1)Mg6 octahedra, and faces with eight equivalent H(2)Mg4 tetrahedra. The corner-sharing octahedra are not tilted. In the second H site, H(2) is bonded to four equivalent Mg(1) atoms to form HMg4 tetrahedra that share corners with twelve equivalent H(1)Mg6 octahedra, corners with sixteen equivalent H(2)Mg4 tetrahedra, edges with six equivalent H(2)Mg4 tetrahedra, and faces with four equivalent H(1)Mg6 octahedra. The corner-sharing octahedral tilt angles are 55°.