K3Ta3Si2O13 crystallizes in the hexagonal P-62m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(3), and eight equivalent O(2) atoms. In the second K site, K(2) is bonded in a 15-coordinate geometry to two equivalent O(3), two equivalent O(4), three equivalent O(5), and eight equivalent O(2) atoms. Ta(1) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 3-31°. Si(1) is bonded to one O(4) and three equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent Ta(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 23°. There are five inequivalent O sites. In the first O site, O(4) is bonded in a linear geometry to three equivalent K(2) and two equivalent Si(1) atoms. In the second O site, O(5) is bonded in a distorted linear geometry to three equivalent K(2) and two equivalent Ta(1) atoms. In the third O site, O(1) is bonded in a linear geometry to two equivalent K(1) and two equivalent Ta(1) atoms. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1), two equivalent K(2), one Ta(1), and one Si(1) atom. In the fifth O site, O(3) is bonded in a 4-coordinate geometry to one K(1), one K(2), and two equivalent Ta(1) atoms.
K3Ta3Si2O13 crystallizes in the hexagonal P-62m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(3), and eight equivalent O(2) atoms. Both K(1)-O(1) bond lengths are 3.22 Å. Both K(1)-O(3) bond lengths are 2.95 Å. There are four shorter (2.97 Å) and four longer (3.09 Å) K(1)-O(2) bond lengths. In the second K site, K(2) is bonded in a 15-coordinate geometry to two equivalent O(3), two equivalent O(4), three equivalent O(5), and eight equivalent O(2) atoms. Both K(2)-O(3) bond lengths are 2.71 Å. Both K(2)-O(4) bond lengths are 2.85 Å. There is one shorter (3.16 Å) and two longer (3.17 Å) K(2)-O(5) bond lengths. There are four shorter (3.26 Å) and four longer (3.27 Å) K(2)-O(2) bond lengths. Ta(1) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 3-31°. The Ta(1)-O(1) bond length is 1.97 Å. The Ta(1)-O(5) bond length is 2.00 Å. Both Ta(1)-O(2) bond lengths are 2.05 Å. Both Ta(1)-O(3) bond lengths are 1.97 Å. Si(1) is bonded to one O(4) and three equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent Ta(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 23°. The Si(1)-O(4) bond length is 1.65 Å. All Si(1)-O(2) bond lengths are 1.62 Å. There are five inequivalent O sites. In the first O site, O(4) is bonded in a linear geometry to three equivalent K(2) and two equivalent Si(1) atoms. In the second O site, O(5) is bonded in a distorted linear geometry to three equivalent K(2) and two equivalent Ta(1) atoms. In the third O site, O(1) is bonded in a linear geometry to two equivalent K(1) and two equivalent Ta(1) atoms. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1), two equivalent K(2), one Ta(1), and one Si(1) atom. In the fifth O site, O(3) is bonded in a 4-coordinate geometry to one K(1), one K(2), and two equivalent Ta(1) atoms.