MgCr2(PO5)2 crystallizes in the tetragonal P-4 space group. Mg(1) is bonded in a 4-coordinate geometry to four equivalent O(3) atoms. Cr(1) is bonded to one O(2), two equivalent O(1), and two equivalent O(3) atoms to form distorted CrO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra and corners with two equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to four equivalent O(1) atoms to form PO4 tetrahedra that share corners with four equivalent Cr(1)O5 trigonal bipyramids. In the second P site, P(2) is bonded to four equivalent O(3) atoms to form PO4 tetrahedra that share corners with four equivalent Cr(1)O5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Cr(1) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Cr(1), and one P(2) atom.
MgCr2(PO5)2 crystallizes in the tetragonal P-4 space group. Mg(1) is bonded in a 4-coordinate geometry to four equivalent O(3) atoms. All Mg(1)-O(3) bond lengths are 2.07 Å. Cr(1) is bonded to one O(2), two equivalent O(1), and two equivalent O(3) atoms to form distorted CrO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra and corners with two equivalent P(2)O4 tetrahedra. The Cr(1)-O(2) bond length is 1.67 Å. Both Cr(1)-O(1) bond lengths are 1.91 Å. Both Cr(1)-O(3) bond lengths are 2.00 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to four equivalent O(1) atoms to form PO4 tetrahedra that share corners with four equivalent Cr(1)O5 trigonal bipyramids. All P(1)-O(1) bond lengths are 1.55 Å. In the second P site, P(2) is bonded to four equivalent O(3) atoms to form PO4 tetrahedra that share corners with four equivalent Cr(1)O5 trigonal bipyramids. All P(2)-O(3) bond lengths are 1.55 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Cr(1) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Cr(1), and one P(2) atom.