SrMgCr(PO4)2 is Esseneite-derived structured and crystallizes in the triclinic P-1 space group. Sr(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(8), two equivalent O(1), and two equivalent O(6) atoms. Mg(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(7), and two equivalent O(5) atoms. Cr(1) is bonded to one O(3), one O(4), one O(5), one O(7), and two equivalent O(8) atoms to form distorted CrO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  an edgeedge with one Cr(1)O6 octahedra, and  an edgeedge with one P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-59°. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Cr(1)O6 octahedra and  an edgeedge with one Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-62°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Sr(1), one Mg(1), and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Sr(1), one Mg(1), and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Sr(1), one Cr(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), one Mg(1), one Cr(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Cr(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to two equivalent Sr(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Mg(1), one Cr(1), and one P(1) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Sr(1), two equivalent Cr(1), and one P(2) atom.
SrMgCr(PO4)2 is Esseneite-derived structured and crystallizes in the triclinic P-1 space group. Sr(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(8), two equivalent O(1), and two equivalent O(6) atoms. The Sr(1)-O(2) bond length is 2.79 Å. The Sr(1)-O(3) bond length is 2.58 Å. The Sr(1)-O(4) bond length is 2.84 Å. The Sr(1)-O(8) bond length is 2.87 Å. There is one shorter (2.59 Å) and one longer (2.66 Å) Sr(1)-O(1) bond length. There is one shorter (2.52 Å) and one longer (2.68 Å) Sr(1)-O(6) bond length. Mg(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(7), and two equivalent O(5) atoms. The Mg(1)-O(1) bond length is 2.62 Å. The Mg(1)-O(2) bond length is 2.02 Å. The Mg(1)-O(4) bond length is 2.09 Å. The Mg(1)-O(7) bond length is 2.03 Å. There is one shorter (2.03 Å) and one longer (2.64 Å) Mg(1)-O(5) bond length. Cr(1) is bonded to one O(3), one O(4), one O(5), one O(7), and two equivalent O(8) atoms to form distorted CrO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  an edgeedge with one Cr(1)O6 octahedra, and  an edgeedge with one P(2)O4 tetrahedra. The Cr(1)-O(3) bond length is 2.08 Å. The Cr(1)-O(4) bond length is 2.14 Å. The Cr(1)-O(5) bond length is 2.43 Å. The Cr(1)-O(7) bond length is 2.03 Å. There is one shorter (2.09 Å) and one longer (2.41 Å) Cr(1)-O(8) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-59°. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(3) bond length is 1.55 Å. The P(1)-O(7) bond length is 1.58 Å. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Cr(1)O6 octahedra and  an edgeedge with one Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-62°. The P(2)-O(4) bond length is 1.60 Å. The P(2)-O(5) bond length is 1.57 Å. The P(2)-O(6) bond length is 1.52 Å. The P(2)-O(8) bond length is 1.56 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Sr(1), one Mg(1), and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Sr(1), one Mg(1), and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Sr(1), one Cr(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), one Mg(1), one Cr(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Cr(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to two equivalent Sr(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Mg(1), one Cr(1), and one P(1) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Sr(1), two equivalent Cr(1), and one P(2) atom.