Sr4Cu2O7 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 8-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to one O(4), two equivalent O(2), two equivalent O(3), and three equivalent O(1) atoms. Cu(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(3) atoms to form corner-sharing CuO5 square pyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), three equivalent Sr(2), and one Cu(1) atom to form distorted OSr5Cu octahedra that share  a cornercorner with one O(2)Sr5Cu octahedra, corners with three equivalent O(4)Sr4Cu2 octahedra, corners with four equivalent O(1)Sr5Cu octahedra, corners with six equivalent O(3)Sr4Cu2 octahedra, edges with two equivalent O(1)Sr5Cu octahedra, edges with six equivalent O(2)Sr5Cu octahedra,  a faceface with one O(4)Sr4Cu2 octahedra, and faces with two equivalent O(3)Sr4Cu2 octahedra. The corner-sharing octahedral tilt angles range from 5-67°. In the second O site, O(2) is bonded to two equivalent Sr(2), three equivalent Sr(1), and one Cu(1) atom to form distorted OSr5Cu octahedra that share  a cornercorner with one O(1)Sr5Cu octahedra, corners with three equivalent O(4)Sr4Cu2 octahedra, corners with four equivalent O(2)Sr5Cu octahedra, corners with six equivalent O(3)Sr4Cu2 octahedra, edges with two equivalent O(2)Sr5Cu octahedra, edges with six equivalent O(1)Sr5Cu octahedra,  a faceface with one O(4)Sr4Cu2 octahedra, and faces with two equivalent O(3)Sr4Cu2 octahedra. The corner-sharing octahedral tilt angles range from 5-67°. In the third O site, O(3) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Cu(1) atoms to form distorted OSr4Cu2 octahedra that share  a cornercorner with one O(4)Sr4Cu2 octahedra, corners with six equivalent O(1)Sr5Cu octahedra, corners with six equivalent O(2)Sr5Cu octahedra,  an edgeedge with one O(4)Sr4Cu2 octahedra,  a faceface with one O(4)Sr4Cu2 octahedra, faces with two equivalent O(3)Sr4Cu2 octahedra, faces with two equivalent O(1)Sr5Cu octahedra, and faces with two equivalent O(2)Sr5Cu octahedra. The corner-sharing octahedral tilt angles range from 2-67°. In the fourth O site, O(4) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Cu(1) atoms to form OSr4Cu2 octahedra that share corners with two equivalent O(3)Sr4Cu2 octahedra, corners with six equivalent O(1)Sr5Cu octahedra, corners with six equivalent O(2)Sr5Cu octahedra, edges with two equivalent O(3)Sr4Cu2 octahedra, faces with two equivalent O(3)Sr4Cu2 octahedra, faces with two equivalent O(1)Sr5Cu octahedra, and faces with two equivalent O(2)Sr5Cu octahedra. The corner-sharing octahedral tilt angles range from 2-63°.
Sr4Cu2O7 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 8-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms. The Sr(1)-O(4) bond length is 2.61 Å. There is one shorter (2.64 Å) and one longer (2.75 Å) Sr(1)-O(1) bond length. There is one shorter (2.47 Å) and one longer (2.68 Å) Sr(1)-O(3) bond length. There are a spread of Sr(1)-O(2) bond distances ranging from 2.49-2.74 Å. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to one O(4), two equivalent O(2), two equivalent O(3), and three equivalent O(1) atoms. The Sr(2)-O(4) bond length is 2.58 Å. There is one shorter (2.66 Å) and one longer (2.74 Å) Sr(2)-O(2) bond length. There is one shorter (2.51 Å) and one longer (2.65 Å) Sr(2)-O(3) bond length. There are a spread of Sr(2)-O(1) bond distances ranging from 2.49-2.75 Å. Cu(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(3) atoms to form corner-sharing CuO5 square pyramids. The Cu(1)-O(1) bond length is 1.90 Å. The Cu(1)-O(2) bond length is 1.90 Å. The Cu(1)-O(4) bond length is 1.88 Å. There is one shorter (1.80 Å) and one longer (2.16 Å) Cu(1)-O(3) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), three equivalent Sr(2), and one Cu(1) atom to form distorted OSr5Cu octahedra that share  a cornercorner with one O(2)Sr5Cu octahedra, corners with three equivalent O(4)Sr4Cu2 octahedra, corners with four equivalent O(1)Sr5Cu octahedra, corners with six equivalent O(3)Sr4Cu2 octahedra, edges with two equivalent O(1)Sr5Cu octahedra, edges with six equivalent O(2)Sr5Cu octahedra,  a faceface with one O(4)Sr4Cu2 octahedra, and faces with two equivalent O(3)Sr4Cu2 octahedra. The corner-sharing octahedral tilt angles range from 5-67°. In the second O site, O(2) is bonded to two equivalent Sr(2), three equivalent Sr(1), and one Cu(1) atom to form distorted OSr5Cu octahedra that share  a cornercorner with one O(1)Sr5Cu octahedra, corners with three equivalent O(4)Sr4Cu2 octahedra, corners with four equivalent O(2)Sr5Cu octahedra, corners with six equivalent O(3)Sr4Cu2 octahedra, edges with two equivalent O(2)Sr5Cu octahedra, edges with six equivalent O(1)Sr5Cu octahedra,  a faceface with one O(4)Sr4Cu2 octahedra, and faces with two equivalent O(3)Sr4Cu2 octahedra. The corner-sharing octahedral tilt angles range from 5-67°. In the third O site, O(3) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Cu(1) atoms to form distorted OSr4Cu2 octahedra that share  a cornercorner with one O(4)Sr4Cu2 octahedra, corners with six equivalent O(1)Sr5Cu octahedra, corners with six equivalent O(2)Sr5Cu octahedra,  an edgeedge with one O(4)Sr4Cu2 octahedra,  a faceface with one O(4)Sr4Cu2 octahedra, faces with two equivalent O(3)Sr4Cu2 octahedra, faces with two equivalent O(1)Sr5Cu octahedra, and faces with two equivalent O(2)Sr5Cu octahedra. The corner-sharing octahedral tilt angles range from 2-67°. In the fourth O site, O(4) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Cu(1) atoms to form OSr4Cu2 octahedra that share corners with two equivalent O(3)Sr4Cu2 octahedra, corners with six equivalent O(1)Sr5Cu octahedra, corners with six equivalent O(2)Sr5Cu octahedra, edges with two equivalent O(3)Sr4Cu2 octahedra, faces with two equivalent O(3)Sr4Cu2 octahedra, faces with two equivalent O(1)Sr5Cu octahedra, and faces with two equivalent O(2)Sr5Cu octahedra. The corner-sharing octahedral tilt angles range from 2-63°.