Ba3Sr4O7 is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form BaO6 octahedra that share corners with two equivalent Ba(1)O6 octahedra, corners with two equivalent Ba(2)O6 octahedra, corners with two equivalent Sr(1)O6 octahedra,  an edgeedge with one Ba(2)O6 octahedra, edges with two equivalent Ba(1)O6 octahedra, edges with four equivalent Sr(2)O6 octahedra, and edges with five equivalent Sr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-6°. In the second Ba site, Ba(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form BaO6 octahedra that share corners with two equivalent Ba(2)O6 octahedra, corners with four equivalent Ba(1)O6 octahedra, edges with two equivalent Ba(1)O6 octahedra, edges with two equivalent Ba(2)O6 octahedra, and edges with eight equivalent Sr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form SrO6 octahedra that share corners with two equivalent Ba(1)O6 octahedra, corners with two equivalent Sr(1)O6 octahedra, corners with two equivalent Sr(2)O6 octahedra,  an edgeedge with one Sr(2)O6 octahedra, edges with five equivalent Ba(1)O6 octahedra, and edges with six equivalent Sr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-8°. In the second Sr site, Sr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form SrO6 octahedra that share corners with two equivalent Sr(1)O6 octahedra, corners with four equivalent Sr(2)O6 octahedra,  an edgeedge with one Sr(1)O6 octahedra, edges with three equivalent Sr(2)O6 octahedra, edges with four equivalent Ba(1)O6 octahedra, and edges with four equivalent Ba(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ba(1), two equivalent Sr(1), and two equivalent Sr(2) atoms to form OBa2Sr4 octahedra that share corners with two equivalent O(1)Ba2Sr4 octahedra, corners with two equivalent O(2)Ba2Sr4 octahedra, corners with two equivalent O(3)Ba2Sr4 octahedra,  an edgeedge with one O(2)Ba2Sr4 octahedra, edges with two equivalent O(1)Ba2Sr4 octahedra, edges with four equivalent O(4)Ba4Sr2 octahedra, and edges with five equivalent O(3)Ba2Sr4 octahedra. The corner-sharing octahedral tilt angles range from 1-5°. In the second O site, O(2) is bonded to two equivalent Ba(2) and four equivalent Sr(2) atoms to form OBa2Sr4 octahedra that share corners with two equivalent O(2)Ba2Sr4 octahedra, corners with four equivalent O(1)Ba2Sr4 octahedra, edges with two equivalent O(1)Ba2Sr4 octahedra, edges with two equivalent O(2)Ba2Sr4 octahedra, and edges with eight equivalent O(4)Ba4Sr2 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the third O site, O(3) is bonded to two equivalent Ba(1) and four equivalent Sr(1) atoms to form OBa2Sr4 octahedra that share corners with two equivalent O(1)Ba2Sr4 octahedra, corners with two equivalent O(3)Ba2Sr4 octahedra, corners with two equivalent O(4)Ba4Sr2 octahedra,  an edgeedge with one O(4)Ba4Sr2 octahedra, edges with five equivalent O(1)Ba2Sr4 octahedra, and edges with six equivalent O(3)Ba2Sr4 octahedra. The corner-sharing octahedral tilt angles range from 2-8°. In the fourth O site, O(4) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Sr(2) atoms to form OBa4Sr2 octahedra that share corners with two equivalent O(3)Ba2Sr4 octahedra, corners with four equivalent O(4)Ba4Sr2 octahedra,  an edgeedge with one O(3)Ba2Sr4 octahedra, edges with three equivalent O(4)Ba4Sr2 octahedra, edges with four equivalent O(1)Ba2Sr4 octahedra, and edges with four equivalent O(2)Ba2Sr4 octahedra. The corner-sharing octahedral tilt angles range from 0-2°.
Ba3Sr4O7 is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form BaO6 octahedra that share corners with two equivalent Ba(1)O6 octahedra, corners with two equivalent Ba(2)O6 octahedra, corners with two equivalent Sr(1)O6 octahedra,  an edgeedge with one Ba(2)O6 octahedra, edges with two equivalent Ba(1)O6 octahedra, edges with four equivalent Sr(2)O6 octahedra, and edges with five equivalent Sr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-6°. Both Ba(1)-O(1) bond lengths are 2.70 Å. Both Ba(1)-O(3) bond lengths are 2.81 Å. Both Ba(1)-O(4) bond lengths are 2.69 Å. In the second Ba site, Ba(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form BaO6 octahedra that share corners with two equivalent Ba(2)O6 octahedra, corners with four equivalent Ba(1)O6 octahedra, edges with two equivalent Ba(1)O6 octahedra, edges with two equivalent Ba(2)O6 octahedra, and edges with eight equivalent Sr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Ba(2)-O(2) bond lengths are 2.70 Å. All Ba(2)-O(4) bond lengths are 2.74 Å. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form SrO6 octahedra that share corners with two equivalent Ba(1)O6 octahedra, corners with two equivalent Sr(1)O6 octahedra, corners with two equivalent Sr(2)O6 octahedra,  an edgeedge with one Sr(2)O6 octahedra, edges with five equivalent Ba(1)O6 octahedra, and edges with six equivalent Sr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-8°. Both Sr(1)-O(1) bond lengths are 2.76 Å. There are two shorter (2.53 Å) and two longer (2.71 Å) Sr(1)-O(3) bond lengths. In the second Sr site, Sr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form SrO6 octahedra that share corners with two equivalent Sr(1)O6 octahedra, corners with four equivalent Sr(2)O6 octahedra,  an edgeedge with one Sr(1)O6 octahedra, edges with three equivalent Sr(2)O6 octahedra, edges with four equivalent Ba(1)O6 octahedra, and edges with four equivalent Ba(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. Both Sr(2)-O(1) bond lengths are 2.64 Å. Both Sr(2)-O(2) bond lengths are 2.70 Å. Both Sr(2)-O(4) bond lengths are 2.70 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ba(1), two equivalent Sr(1), and two equivalent Sr(2) atoms to form OBa2Sr4 octahedra that share corners with two equivalent O(1)Ba2Sr4 octahedra, corners with two equivalent O(2)Ba2Sr4 octahedra, corners with two equivalent O(3)Ba2Sr4 octahedra,  an edgeedge with one O(2)Ba2Sr4 octahedra, edges with two equivalent O(1)Ba2Sr4 octahedra, edges with four equivalent O(4)Ba4Sr2 octahedra, and edges with five equivalent O(3)Ba2Sr4 octahedra. The corner-sharing octahedral tilt angles range from 1-5°. In the second O site, O(2) is bonded to two equivalent Ba(2) and four equivalent Sr(2) atoms to form OBa2Sr4 octahedra that share corners with two equivalent O(2)Ba2Sr4 octahedra, corners with four equivalent O(1)Ba2Sr4 octahedra, edges with two equivalent O(1)Ba2Sr4 octahedra, edges with two equivalent O(2)Ba2Sr4 octahedra, and edges with eight equivalent O(4)Ba4Sr2 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the third O site, O(3) is bonded to two equivalent Ba(1) and four equivalent Sr(1) atoms to form OBa2Sr4 octahedra that share corners with two equivalent O(1)Ba2Sr4 octahedra, corners with two equivalent O(3)Ba2Sr4 octahedra, corners with two equivalent O(4)Ba4Sr2 octahedra,  an edgeedge with one O(4)Ba4Sr2 octahedra, edges with five equivalent O(1)Ba2Sr4 octahedra, and edges with six equivalent O(3)Ba2Sr4 octahedra. The corner-sharing octahedral tilt angles range from 2-8°. In the fourth O site, O(4) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Sr(2) atoms to form OBa4Sr2 octahedra that share corners with two equivalent O(3)Ba2Sr4 octahedra, corners with four equivalent O(4)Ba4Sr2 octahedra,  an edgeedge with one O(3)Ba2Sr4 octahedra, edges with three equivalent O(4)Ba4Sr2 octahedra, edges with four equivalent O(1)Ba2Sr4 octahedra, and edges with four equivalent O(2)Ba2Sr4 octahedra. The corner-sharing octahedral tilt angles range from 0-2°.