Mg2(PO4)OH crystallizes in the orthorhombic Pnma space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(3) atoms to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent P(1)O4 tetrahedra, and edges with two equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent P(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Mg(2)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. P(1) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with four equivalent Mg(2)O6 octahedra and corners with four equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 47-57°. H(1) is bonded in a single-bond geometry to one O(1) atom. There are four inequivalent O sites. In the first O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one P(1) atom. In the second O site, O(1) is bonded in a distorted single-bond geometry to one Mg(1), two equivalent Mg(2), and one H(1) atom. In the third O site, O(2) is bonded in a linear geometry to one Mg(1) and one P(1) atom. In the fourth O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom.
Mg2(PO4)OH crystallizes in the orthorhombic Pnma space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(3) atoms to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent P(1)O4 tetrahedra, and edges with two equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. The Mg(1)-O(1) bond length is 2.07 Å. The Mg(1)-O(2) bond length is 1.92 Å. The Mg(1)-O(4) bond length is 2.16 Å. Both Mg(1)-O(3) bond lengths are 2.03 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent P(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Mg(2)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. Both Mg(2)-O(1) bond lengths are 2.09 Å. Both Mg(2)-O(3) bond lengths are 2.06 Å. Both Mg(2)-O(4) bond lengths are 2.11 Å. P(1) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with four equivalent Mg(2)O6 octahedra and corners with four equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 47-57°. The P(1)-O(2) bond length is 1.50 Å. The P(1)-O(4) bond length is 1.56 Å. Both P(1)-O(3) bond lengths are 1.54 Å. H(1) is bonded in a single-bond geometry to one O(1) atom. The H(1)-O(1) bond length is 0.97 Å. There are four inequivalent O sites. In the first O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one P(1) atom. In the second O site, O(1) is bonded in a distorted single-bond geometry to one Mg(1), two equivalent Mg(2), and one H(1) atom. In the third O site, O(2) is bonded in a linear geometry to one Mg(1) and one P(1) atom. In the fourth O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom.