Mg2NiH4 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent H(1), two equivalent H(2), two equivalent H(3), and two equivalent H(4) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a square co-planar geometry to two equivalent H(1) and two equivalent H(2) atoms. In the second Ni site, Ni(2) is bonded in a square co-planar geometry to two equivalent H(3) and two equivalent H(4) atoms. There are four inequivalent H sites. In the first H site, H(1) is bonded to four equivalent Mg(1) and one Ni(1) atom to form a mixture of distorted corner and edge-sharing HMg4Ni square pyramids. In the second H site, H(2) is bonded in a 1-coordinate geometry to four equivalent Mg(1) and one Ni(1) atom. In the third H site, H(3) is bonded to four equivalent Mg(1) and one Ni(2) atom to form a mixture of distorted corner, face, and edge-sharing HMg4Ni square pyramids. In the fourth H site, H(4) is bonded to four equivalent Mg(1) and one Ni(2) atom to form a mixture of distorted corner, face, and edge-sharing HMg4Ni square pyramids.
Mg2NiH4 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent H(1), two equivalent H(2), two equivalent H(3), and two equivalent H(4) atoms. There is one shorter (2.27 Å) and one longer (2.29 Å) Mg(1)-H(1) bond length. There is one shorter (2.24 Å) and one longer (2.39 Å) Mg(1)-H(2) bond length. There is one shorter (2.16 Å) and one longer (2.27 Å) Mg(1)-H(3) bond length. There is one shorter (2.19 Å) and one longer (2.34 Å) Mg(1)-H(4) bond length. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a square co-planar geometry to two equivalent H(1) and two equivalent H(2) atoms. Both Ni(1)-H(1) bond lengths are 1.53 Å. Both Ni(1)-H(2) bond lengths are 1.54 Å. In the second Ni site, Ni(2) is bonded in a square co-planar geometry to two equivalent H(3) and two equivalent H(4) atoms. Both Ni(2)-H(3) bond lengths are 1.54 Å. Both Ni(2)-H(4) bond lengths are 1.55 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded to four equivalent Mg(1) and one Ni(1) atom to form a mixture of distorted corner and edge-sharing HMg4Ni square pyramids. In the second H site, H(2) is bonded in a 1-coordinate geometry to four equivalent Mg(1) and one Ni(1) atom. In the third H site, H(3) is bonded to four equivalent Mg(1) and one Ni(2) atom to form a mixture of distorted corner, face, and edge-sharing HMg4Ni square pyramids. In the fourth H site, H(4) is bonded to four equivalent Mg(1) and one Ni(2) atom to form a mixture of distorted corner, face, and edge-sharing HMg4Ni square pyramids.