Sr3Cu3(PO4)4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(5), one O(6), one O(8), two equivalent O(4), and two equivalent O(7) atoms. In the second Sr site, Sr(2) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(8) atoms to form distorted SrO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra, and edges with two equivalent Cu(1)O5 trigonal bipyramids. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(6) atom to form CuO5 trigonal bipyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Sr(2)O6 octahedra. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. There are two inequivalent P sites. In the first P site, P(1) 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 Sr(2)O6 octahedra and corners with three equivalent Cu(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 41-59°. In the second P site, P(2) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Sr(2)O6 octahedra and corners with two equivalent Cu(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 56°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Sr(1), one Cu(1), one Cu(2), and one P(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Sr(1), one Cu(2), and one P(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Sr(2), one Cu(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Sr(1), one Cu(1), and one P(1) atom. In the fifth O site, O(5) is bonded to one Sr(1), one Sr(2), one Cu(1), and one P(1) atom to form distorted corner-sharing OSr2CuP tetrahedra. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Sr(1), one Cu(1), and one P(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Sr(1) and one P(2) atom. In the eighth O site, O(8) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(2), and one P(1) atom.
Sr3Cu3(PO4)4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(5), one O(6), one O(8), two equivalent O(4), and two equivalent O(7) atoms. The Sr(1)-O(1) bond length is 2.72 Å. The Sr(1)-O(2) bond length is 2.57 Å. The Sr(1)-O(5) bond length is 2.66 Å. The Sr(1)-O(6) bond length is 2.73 Å. The Sr(1)-O(8) bond length is 2.95 Å. There is one shorter (2.54 Å) and one longer (3.04 Å) Sr(1)-O(4) bond length. There is one shorter (2.52 Å) and one longer (2.84 Å) Sr(1)-O(7) bond length. In the second Sr site, Sr(2) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(8) atoms to form distorted SrO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra, and edges with two equivalent Cu(1)O5 trigonal bipyramids. Both Sr(2)-O(3) bond lengths are 2.50 Å. Both Sr(2)-O(5) bond lengths are 2.56 Å. Both Sr(2)-O(8) bond lengths are 2.46 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(6) atom to form CuO5 trigonal bipyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Sr(2)O6 octahedra. The Cu(1)-O(1) bond length is 2.16 Å. The Cu(1)-O(3) bond length is 1.97 Å. The Cu(1)-O(4) bond length is 1.93 Å. The Cu(1)-O(5) bond length is 2.25 Å. The Cu(1)-O(6) bond length is 2.03 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. Both Cu(2)-O(1) bond lengths are 1.98 Å. Both Cu(2)-O(2) bond lengths are 1.97 Å. There are two inequivalent P sites. In the first P site, P(1) 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 Sr(2)O6 octahedra and corners with three equivalent Cu(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 41-59°. The P(1)-O(4) bond length is 1.58 Å. The P(1)-O(5) bond length is 1.56 Å. The P(1)-O(6) bond length is 1.56 Å. The P(1)-O(8) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Sr(2)O6 octahedra and corners with two equivalent Cu(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 56°. The P(2)-O(1) bond length is 1.59 Å. The P(2)-O(2) bond length is 1.56 Å. The P(2)-O(3) bond length is 1.55 Å. The P(2)-O(7) bond length is 1.53 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Sr(1), one Cu(1), one Cu(2), and one P(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Sr(1), one Cu(2), and one P(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Sr(2), one Cu(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Sr(1), one Cu(1), and one P(1) atom. In the fifth O site, O(5) is bonded to one Sr(1), one Sr(2), one Cu(1), and one P(1) atom to form distorted corner-sharing OSr2CuP tetrahedra. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Sr(1), one Cu(1), and one P(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Sr(1) and one P(2) atom. In the eighth O site, O(8) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(2), and one P(1) atom.