Li2SrTa2O7 crystallizes in the orthorhombic Cmcm space group. Li(1) is bonded to one O(3) and four equivalent O(2) atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Sr(1)O12 cuboctahedra, corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Li(1)O5 trigonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with four equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 66°. Sr(1) is bonded to four equivalent O(1), four equivalent O(3), and four equivalent O(4) atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra, corners with four equivalent Li(1)O5 trigonal bipyramids, faces with four equivalent Sr(1)O12 cuboctahedra, and faces with eight equivalent Ta(1)O6 octahedra. Ta(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with five equivalent Ta(1)O6 octahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, edges with two equivalent Li(1)O5 trigonal bipyramids, and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-20°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1) and two equivalent Ta(1) atoms to form distorted OSr2Ta2 trigonal pyramids that share corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(1)Sr2Ta2 trigonal pyramids, and edges with three equivalent O(1)Sr2Ta2 trigonal pyramids. In the second O site, O(2) is bonded to four equivalent Li(1) and one Ta(1) atom to form distorted OLi4Ta trigonal bipyramids that share corners with four equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(1)Sr2Ta2 trigonal pyramids, and edges with four equivalent O(2)Li4Ta trigonal bipyramids. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Li(1), two equivalent Sr(1), and two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to four equivalent Sr(1) and two equivalent Ta(1) atoms.
Li2SrTa2O7 crystallizes in the orthorhombic Cmcm space group. Li(1) is bonded to one O(3) and four equivalent O(2) atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Sr(1)O12 cuboctahedra, corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Li(1)O5 trigonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with four equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 66°. The Li(1)-O(3) bond length is 2.24 Å. There are two shorter (2.00 Å) and two longer (2.12 Å) Li(1)-O(2) bond lengths. Sr(1) is bonded to four equivalent O(1), four equivalent O(3), and four equivalent O(4) atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra, corners with four equivalent Li(1)O5 trigonal bipyramids, 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 2.64 Å. All Sr(1)-O(3) bond lengths are 2.85 Å. There are a spread of Sr(1)-O(4) bond distances ranging from 2.54-3.04 Å. Ta(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with five equivalent Ta(1)O6 octahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, edges with two equivalent Li(1)O5 trigonal bipyramids, and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-20°. The Ta(1)-O(2) bond length is 1.86 Å. The Ta(1)-O(4) bond length is 2.11 Å. Both Ta(1)-O(1) bond lengths are 1.99 Å. Both Ta(1)-O(3) bond lengths are 1.98 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1) and two equivalent Ta(1) atoms to form distorted OSr2Ta2 trigonal pyramids that share corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(1)Sr2Ta2 trigonal pyramids, and edges with three equivalent O(1)Sr2Ta2 trigonal pyramids. In the second O site, O(2) is bonded to four equivalent Li(1) and one Ta(1) atom to form distorted OLi4Ta trigonal bipyramids that share corners with four equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(1)Sr2Ta2 trigonal pyramids, and edges with four equivalent O(2)Li4Ta trigonal bipyramids. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Li(1), two equivalent Sr(1), and two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to four equivalent Sr(1) and two equivalent Ta(1) atoms.