MgH2(SeO4)2 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra. H(1) is bonded in a distorted linear geometry to one O(1) and one O(4) atom. Se(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SeO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-47°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one H(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Mg(1) and one Se(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one H(1), and one Se(1) atom.
MgH2(SeO4)2 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra. Both Mg(1)-O(2) bond lengths are 2.09 Å. Both Mg(1)-O(3) bond lengths are 2.09 Å. Both Mg(1)-O(4) bond lengths are 2.15 Å. H(1) is bonded in a distorted linear geometry to one O(1) and one O(4) atom. The H(1)-O(1) bond length is 1.02 Å. The H(1)-O(4) bond length is 1.64 Å. Se(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SeO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-47°. The Se(1)-O(1) bond length is 1.75 Å. The Se(1)-O(2) bond length is 1.65 Å. The Se(1)-O(3) bond length is 1.64 Å. The Se(1)-O(4) bond length is 1.67 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one H(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Mg(1) and one Se(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one H(1), and one Se(1) atom.