K2SrTa2O7 crystallizes in the tetragonal I4/mmm space group. K(1) is bonded in a 9-coordinate geometry to four equivalent O(3) and five equivalent O(2) atoms. Sr(1) is bonded to four equivalent O(1) and eight equivalent O(3) atoms to form SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra, faces with four equivalent Sr(1)O12 cuboctahedra, and faces with eight equivalent Ta(1)O6 octahedra. Ta(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form TaO6 octahedra that share corners with five equivalent Ta(1)O6 octahedra and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-11°. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Sr(1) and two equivalent Ta(1) atoms to form distorted OSr4Ta2 octahedra that share corners with two equivalent O(2)K5Ta octahedra, corners with four equivalent O(1)Sr4Ta2 octahedra, and edges with four equivalent O(1)Sr4Ta2 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded to five equivalent K(1) and one Ta(1) atom to form distorted OK5Ta octahedra that share  a cornercorner with one O(1)Sr4Ta2 octahedra, corners with four equivalent O(2)K5Ta octahedra, and edges with eight equivalent O(2)K5Ta octahedra. The corner-sharing octahedral tilt angles range from 0-11°. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent K(1), two equivalent Sr(1), and two equivalent Ta(1) atoms.
K2SrTa2O7 crystallizes in the tetragonal I4/mmm space group. K(1) is bonded in a 9-coordinate geometry to four equivalent O(3) and five equivalent O(2) atoms. All K(1)-O(3) bond lengths are 3.08 Å. There is one shorter (2.78 Å) and four longer (2.85 Å) K(1)-O(2) bond lengths. Sr(1) is bonded to four equivalent O(1) and eight equivalent O(3) atoms to form SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra, faces with four equivalent Sr(1)O12 cuboctahedra, and faces with eight equivalent Ta(1)O6 octahedra. All Sr(1)-O(1) bond lengths are 2.84 Å. All Sr(1)-O(3) bond lengths are 2.79 Å. Ta(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form TaO6 octahedra that share corners with five equivalent Ta(1)O6 octahedra and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-11°. The Ta(1)-O(1) bond length is 2.12 Å. The Ta(1)-O(2) bond length is 1.87 Å. All Ta(1)-O(3) bond lengths are 2.02 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Sr(1) and two equivalent Ta(1) atoms to form distorted OSr4Ta2 octahedra that share corners with two equivalent O(2)K5Ta octahedra, corners with four equivalent O(1)Sr4Ta2 octahedra, and edges with four equivalent O(1)Sr4Ta2 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded to five equivalent K(1) and one Ta(1) atom to form distorted OK5Ta octahedra that share  a cornercorner with one O(1)Sr4Ta2 octahedra, corners with four equivalent O(2)K5Ta octahedra, and edges with eight equivalent O(2)K5Ta octahedra. The corner-sharing octahedral tilt angles range from 0-11°. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent K(1), two equivalent Sr(1), and two equivalent Ta(1) atoms.