MgNiAsO5 crystallizes in the orthorhombic P2_12_12_1 space group. Mg(1) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(5), and two equivalent O(4) atoms. Ni(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(5) atoms to form NiO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra and edges with two equivalent Ni(1)O6 octahedra. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-64°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ni(1) and one As(1) atom. In the second O site, O(2) is bonded in a water-like geometry to one Mg(1) and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Ni(1), and one As(1) atom. In the fifth O site, O(5) is bonded in a trigonal non-coplanar geometry to one Mg(1) and two equivalent Ni(1) atoms.
MgNiAsO5 crystallizes in the orthorhombic P2_12_12_1 space group. Mg(1) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(5), and two equivalent O(4) atoms. The Mg(1)-O(2) bond length is 2.05 Å. The Mg(1)-O(3) bond length is 2.13 Å. The Mg(1)-O(5) bond length is 2.01 Å. There is one shorter (2.29 Å) and one longer (2.61 Å) Mg(1)-O(4) bond length. Ni(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(5) atoms to form NiO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra and edges with two equivalent Ni(1)O6 octahedra. The Ni(1)-O(3) bond length is 2.02 Å. The Ni(1)-O(4) bond length is 2.02 Å. Both Ni(1)-O(1) bond lengths are 2.02 Å. There is one shorter (1.85 Å) and one longer (1.86 Å) Ni(1)-O(5) bond length. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-64°. The As(1)-O(1) bond length is 1.72 Å. The As(1)-O(2) bond length is 1.70 Å. The As(1)-O(3) bond length is 1.72 Å. The As(1)-O(4) bond length is 1.73 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ni(1) and one As(1) atom. In the second O site, O(2) is bonded in a water-like geometry to one Mg(1) and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Ni(1), and one As(1) atom. In the fifth O site, O(5) is bonded in a trigonal non-coplanar geometry to one Mg(1) and two equivalent Ni(1) atoms.