SrTl3O5 crystallizes in the orthorhombic Cmcm space group. Sr(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(1) atoms. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles are 9°. In the second Tl site, Tl(2) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles range from 9-57°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), one Tl(1), and two equivalent Tl(2) atoms to form distorted OSr2Tl3 trigonal bipyramids that share corners with four equivalent O(3)Tl5 square pyramids, corners with four equivalent O(2)Sr2Tl2 tetrahedra, corners with three equivalent O(1)Sr2Tl3 trigonal bipyramids, edges with three equivalent O(3)Tl5 square pyramids,  an edgeedge with one O(2)Sr2Tl2 tetrahedra, and edges with three equivalent O(1)Sr2Tl3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Sr(1) and two equivalent Tl(2) atoms to form OSr2Tl2 tetrahedra that share corners with six equivalent O(3)Tl5 square pyramids, corners with two equivalent O(2)Sr2Tl2 tetrahedra, corners with eight equivalent O(1)Sr2Tl3 trigonal bipyramids, and edges with two equivalent O(1)Sr2Tl3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Tl(1) and three equivalent Tl(2) atoms to form distorted OTl5 square pyramids that share corners with two equivalent O(3)Tl5 square pyramids, corners with three equivalent O(2)Sr2Tl2 tetrahedra, corners with four equivalent O(1)Sr2Tl3 trigonal bipyramids, edges with five equivalent O(3)Tl5 square pyramids, and edges with three equivalent O(1)Sr2Tl3 trigonal bipyramids.
SrTl3O5 crystallizes in the orthorhombic Cmcm space group. Sr(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(1) atoms. Both Sr(1)-O(2) bond lengths are 2.50 Å. All Sr(1)-O(1) bond lengths are 2.67 Å. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles are 9°. Both Tl(1)-O(1) bond lengths are 2.21 Å. All Tl(1)-O(3) bond lengths are 2.51 Å. In the second Tl site, Tl(2) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles range from 9-57°. The Tl(2)-O(2) bond length is 2.23 Å. Both Tl(2)-O(1) bond lengths are 2.46 Å. There is one shorter (2.36 Å) and two longer (2.50 Å) Tl(2)-O(3) bond lengths. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), one Tl(1), and two equivalent Tl(2) atoms to form distorted OSr2Tl3 trigonal bipyramids that share corners with four equivalent O(3)Tl5 square pyramids, corners with four equivalent O(2)Sr2Tl2 tetrahedra, corners with three equivalent O(1)Sr2Tl3 trigonal bipyramids, edges with three equivalent O(3)Tl5 square pyramids,  an edgeedge with one O(2)Sr2Tl2 tetrahedra, and edges with three equivalent O(1)Sr2Tl3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Sr(1) and two equivalent Tl(2) atoms to form OSr2Tl2 tetrahedra that share corners with six equivalent O(3)Tl5 square pyramids, corners with two equivalent O(2)Sr2Tl2 tetrahedra, corners with eight equivalent O(1)Sr2Tl3 trigonal bipyramids, and edges with two equivalent O(1)Sr2Tl3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Tl(1) and three equivalent Tl(2) atoms to form distorted OTl5 square pyramids that share corners with two equivalent O(3)Tl5 square pyramids, corners with three equivalent O(2)Sr2Tl2 tetrahedra, corners with four equivalent O(1)Sr2Tl3 trigonal bipyramids, edges with five equivalent O(3)Tl5 square pyramids, and edges with three equivalent O(1)Sr2Tl3 trigonal bipyramids.