Sr4CaFe2(SO3)2 crystallizes in the tetragonal P-4m2 space group. There are four inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to four equivalent S(1), two equivalent O(1), and two equivalent O(2) atoms. In the second Sr site, Sr(1) is bonded in a 8-coordinate geometry to four equivalent S(1), two equivalent O(1), and two equivalent O(2) atoms. In the third Sr site, Sr(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), and five equivalent O(3) atoms. In the fourth Sr site, Sr(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), and five equivalent O(3) atoms. Ca(1) is bonded to four equivalent S(1) atoms to form distorted corner-sharing CaS4 tetrahedra. Fe(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form corner-sharing FeO5 square pyramids. S(1) is bonded in a 6-coordinate geometry to four equivalent Sr(1) and two equivalent Ca(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with two equivalent O(1)Sr4Fe2 octahedra, corners with six equivalent O(3)Sr5Fe octahedra, edges with two equivalent O(1)Sr4Fe2 octahedra, faces with two equivalent O(3)Sr5Fe octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 19-55°. In the second O site, O(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with two equivalent O(2)Sr4Fe2 octahedra, corners with six equivalent O(3)Sr5Fe octahedra, edges with two equivalent O(2)Sr4Fe2 octahedra, faces with two equivalent O(3)Sr5Fe octahedra, and faces with four equivalent O(1)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 19-55°. In the third O site, O(3) is bonded to five Sr(2,2) and one Fe(1) atom to form distorted OSr5Fe octahedra that share corners with four equivalent O(3)Sr5Fe octahedra, corners with six equivalent O(1)Sr4Fe2 octahedra, corners with six equivalent O(2)Sr4Fe2 octahedra, edges with eight equivalent O(3)Sr5Fe octahedra, faces with two equivalent O(1)Sr4Fe2 octahedra, and faces with two equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 12-55°.
Sr4CaFe2(SO3)2 crystallizes in the tetragonal P-4m2 space group. There are four inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to four equivalent S(1), two equivalent O(1), and two equivalent O(2) atoms. All Sr(1)-S(1) bond lengths are 3.21 Å. Both Sr(1)-O(1) bond lengths are 2.57 Å. Both Sr(1)-O(2) bond lengths are 2.57 Å. In the second Sr site, Sr(1) is bonded in a 8-coordinate geometry to four equivalent S(1), two equivalent O(1), and two equivalent O(2) atoms. All Sr(1)-S(1) bond lengths are 3.21 Å. Both Sr(1)-O(1) bond lengths are 2.57 Å. Both Sr(1)-O(2) bond lengths are 2.57 Å. In the third Sr site, Sr(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), and five equivalent O(3) atoms. Both Sr(2)-O(1) bond lengths are 2.79 Å. Both Sr(2)-O(2) bond lengths are 2.80 Å. There is one shorter (2.48 Å) and four longer (2.83 Å) Sr(2)-O(3) bond lengths. In the fourth Sr site, Sr(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), and five equivalent O(3) atoms. Both Sr(2)-O(1) bond lengths are 2.79 Å. Both Sr(2)-O(2) bond lengths are 2.80 Å. There is one shorter (2.48 Å) and four longer (2.83 Å) Sr(2)-O(3) bond lengths. Ca(1) is bonded to four equivalent S(1) atoms to form distorted corner-sharing CaS4 tetrahedra. All Ca(1)-S(1) bond lengths are 2.72 Å. Fe(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form corner-sharing FeO5 square pyramids. The Fe(1)-O(3) bond length is 1.92 Å. Both Fe(1)-O(1) bond lengths are 2.02 Å. Both Fe(1)-O(2) bond lengths are 2.02 Å. S(1) is bonded in a 6-coordinate geometry to four equivalent Sr(1) and two equivalent Ca(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with two equivalent O(1)Sr4Fe2 octahedra, corners with six equivalent O(3)Sr5Fe octahedra, edges with two equivalent O(1)Sr4Fe2 octahedra, faces with two equivalent O(3)Sr5Fe octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 19-55°. In the second O site, O(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with two equivalent O(2)Sr4Fe2 octahedra, corners with six equivalent O(3)Sr5Fe octahedra, edges with two equivalent O(2)Sr4Fe2 octahedra, faces with two equivalent O(3)Sr5Fe octahedra, and faces with four equivalent O(1)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 19-55°. In the third O site, O(3) is bonded to five Sr(2,2) and one Fe(1) atom to form distorted OSr5Fe octahedra that share corners with four equivalent O(3)Sr5Fe octahedra, corners with six equivalent O(1)Sr4Fe2 octahedra, corners with six equivalent O(2)Sr4Fe2 octahedra, edges with eight equivalent O(3)Sr5Fe octahedra, faces with two equivalent O(1)Sr4Fe2 octahedra, and faces with two equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 12-55°.