Li2CaTa2O7 crystallizes in the orthorhombic Pnma 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 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 59°. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(4) atoms. Ta(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with five equivalent Ta(1)O6 octahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and edges with two equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 22-31°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Li(1), one Ca(1), and two equivalent Ta(1) atoms. In the second O site, O(4) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 trigonal pyramids that share corners with four equivalent O(1)Ca2Ta2 tetrahedra, corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(4)Ca2Ta2 trigonal pyramids,  an edgeedge with one O(1)Ca2Ta2 tetrahedra, and edges with three equivalent O(4)Ca2Ta2 trigonal pyramids. In the third O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 tetrahedra that share corners with two equivalent O(1)Ca2Ta2 tetrahedra, corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with eight equivalent O(4)Ca2Ta2 trigonal pyramids, and edges with two equivalent O(4)Ca2Ta2 trigonal pyramids. In the fourth O site, O(2) is bonded to four equivalent Li(1) and one Ta(1) atom to form distorted OLi4Ta trigonal bipyramids that share  a cornercorner with one O(1)Ca2Ta2 tetrahedra, corners with four equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(4)Ca2Ta2 trigonal pyramids, and edges with four equivalent O(2)Li4Ta trigonal bipyramids.
Li2CaTa2O7 crystallizes in the orthorhombic Pnma 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 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 59°. The Li(1)-O(3) bond length is 2.17 Å. There are a spread of Li(1)-O(2) bond distances ranging from 1.96-2.22 Å. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(4) atoms. There is one shorter (2.33 Å) and one longer (2.45 Å) Ca(1)-O(1) bond length. Both Ca(1)-O(3) bond lengths are 2.61 Å. There are two shorter (2.43 Å) and two longer (2.54 Å) Ca(1)-O(4) bond lengths. Ta(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with five equivalent Ta(1)O6 octahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and edges with two equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 22-31°. The Ta(1)-O(1) bond length is 2.10 Å. The Ta(1)-O(2) bond length is 1.87 Å. There is one shorter (1.95 Å) and one longer (2.02 Å) Ta(1)-O(3) bond length. There is one shorter (1.97 Å) and one longer (2.04 Å) Ta(1)-O(4) bond length. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Li(1), one Ca(1), and two equivalent Ta(1) atoms. In the second O site, O(4) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 trigonal pyramids that share corners with four equivalent O(1)Ca2Ta2 tetrahedra, corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(4)Ca2Ta2 trigonal pyramids,  an edgeedge with one O(1)Ca2Ta2 tetrahedra, and edges with three equivalent O(4)Ca2Ta2 trigonal pyramids. In the third O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 tetrahedra that share corners with two equivalent O(1)Ca2Ta2 tetrahedra, corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with eight equivalent O(4)Ca2Ta2 trigonal pyramids, and edges with two equivalent O(4)Ca2Ta2 trigonal pyramids. In the fourth O site, O(2) is bonded to four equivalent Li(1) and one Ta(1) atom to form distorted OLi4Ta trigonal bipyramids that share  a cornercorner with one O(1)Ca2Ta2 tetrahedra, corners with four equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(4)Ca2Ta2 trigonal pyramids, and edges with four equivalent O(2)Li4Ta trigonal bipyramids.