Sr3InP3 crystallizes in the orthorhombic Pnma space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent P(1) and three equivalent P(3) atoms to form distorted SrP5 square pyramids that share corners with two equivalent In(1)P4 tetrahedra, edges with four equivalent Sr(1)P5 square pyramids, and edges with three equivalent In(1)P4 tetrahedra. In the second Sr site, Sr(2) is bonded in a 5-coordinate geometry to one P(3), two equivalent P(1), and two equivalent P(2) atoms. In the third Sr site, Sr(3) is bonded in a 6-coordinate geometry to one P(3), two equivalent P(1), and three equivalent P(2) atoms. In(1) is bonded to one P(1), one P(2), and two equivalent P(3) atoms to form distorted InP4 tetrahedra that share corners with two equivalent Sr(1)P5 square pyramids, corners with two equivalent In(1)P4 tetrahedra, and edges with three equivalent Sr(1)P5 square pyramids. There are three inequivalent P sites. In the first P site, P(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), two equivalent Sr(3), and one In(1) atom to form distorted PSr6In pentagonal bipyramids that share corners with six equivalent P(2)Sr5In octahedra,  an edgeedge with one P(2)Sr5In octahedra,  a faceface with one P(2)Sr5In octahedra, and faces with two equivalent P(1)Sr6In pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 9-88°. In the second P site, P(2) is bonded to two equivalent Sr(2), three equivalent Sr(3), and one In(1) atom to form distorted PSr5In octahedra that share corners with six equivalent P(1)Sr6In pentagonal bipyramids, edges with four equivalent P(2)Sr5In octahedra,  an edgeedge with one P(1)Sr6In pentagonal bipyramid, and  a faceface with one P(1)Sr6In pentagonal bipyramid. In the third P site, P(3) is bonded in a 7-coordinate geometry to one Sr(2), one Sr(3), three equivalent Sr(1), and two equivalent In(1) atoms.
Sr3InP3 crystallizes in the orthorhombic Pnma space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent P(1) and three equivalent P(3) atoms to form distorted SrP5 square pyramids that share corners with two equivalent In(1)P4 tetrahedra, edges with four equivalent Sr(1)P5 square pyramids, and edges with three equivalent In(1)P4 tetrahedra. Both Sr(1)-P(1) bond lengths are 3.05 Å. There is one shorter (3.13 Å) and two longer (3.24 Å) Sr(1)-P(3) bond lengths. In the second Sr site, Sr(2) is bonded in a 5-coordinate geometry to one P(3), two equivalent P(1), and two equivalent P(2) atoms. The Sr(2)-P(3) bond length is 3.06 Å. Both Sr(2)-P(1) bond lengths are 3.17 Å. Both Sr(2)-P(2) bond lengths are 3.03 Å. In the third Sr site, Sr(3) is bonded in a 6-coordinate geometry to one P(3), two equivalent P(1), and three equivalent P(2) atoms. The Sr(3)-P(3) bond length is 3.52 Å. Both Sr(3)-P(1) bond lengths are 3.25 Å. There are two shorter (3.07 Å) and one longer (3.08 Å) Sr(3)-P(2) bond length. In(1) is bonded to one P(1), one P(2), and two equivalent P(3) atoms to form distorted InP4 tetrahedra that share corners with two equivalent Sr(1)P5 square pyramids, corners with two equivalent In(1)P4 tetrahedra, and edges with three equivalent Sr(1)P5 square pyramids. The In(1)-P(1) bond length is 2.63 Å. The In(1)-P(2) bond length is 2.60 Å. Both In(1)-P(3) bond lengths are 2.64 Å. There are three inequivalent P sites. In the first P site, P(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), two equivalent Sr(3), and one In(1) atom to form distorted PSr6In pentagonal bipyramids that share corners with six equivalent P(2)Sr5In octahedra,  an edgeedge with one P(2)Sr5In octahedra,  a faceface with one P(2)Sr5In octahedra, and faces with two equivalent P(1)Sr6In pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 9-88°. In the second P site, P(2) is bonded to two equivalent Sr(2), three equivalent Sr(3), and one In(1) atom to form distorted PSr5In octahedra that share corners with six equivalent P(1)Sr6In pentagonal bipyramids, edges with four equivalent P(2)Sr5In octahedra,  an edgeedge with one P(1)Sr6In pentagonal bipyramid, and  a faceface with one P(1)Sr6In pentagonal bipyramid. In the third P site, P(3) is bonded in a 7-coordinate geometry to one Sr(2), one Sr(3), three equivalent Sr(1), and two equivalent In(1) atoms.