K4BaTa6(Si2O13)2 crystallizes in the orthorhombic Amm2 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 4-coordinate geometry to two equivalent O(5) and two equivalent O(6) atoms. In the second K site, K(2) is bonded in a 13-coordinate geometry to one O(2), two equivalent O(3), two equivalent O(4), two equivalent O(6), two equivalent O(8), and four equivalent O(7) atoms. Ba(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(8), four equivalent O(3), and four equivalent O(4) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(3), one O(6), one O(7), one O(8), and one O(9) atom to form TaO6 octahedra that share  a cornercorner with one Ta(2)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 3-32°. In the second Ta site, Ta(2) is bonded to one O(10), one O(2), two equivalent O(4), and two equivalent O(6) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 2-32°. Si(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ta(2)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-27°. There are ten inequivalent O sites. In the first O site, O(3) is bonded in a distorted bent 150 degrees geometry to one K(2), one Ba(1), one Ta(1), and one Si(1) atom. In the second O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(2), one Ba(1), one Ta(2), and one Si(1) atom. In the third O site, O(5) is bonded in a distorted linear geometry to two equivalent K(1) and two equivalent Si(1) atoms. In the fourth O site, O(6) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Ta(1), and one Ta(2) atom. In the fifth O site, O(7) is bonded in a distorted bent 150 degrees geometry to two equivalent K(2), one Ta(1), and one Si(1) atom. In the sixth O site, O(8) is bonded in a linear geometry to two equivalent K(2), one Ba(1), and two equivalent Ta(1) atoms. In the seventh O site, O(9) is bonded in a distorted linear geometry to two equivalent Ta(1) atoms. In the eighth O site, O(10) is bonded in a distorted linear geometry to two equivalent Ta(2) atoms. In the ninth O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and two equivalent Ta(1) atoms. In the tenth O site, O(2) is bonded in a linear geometry to two equivalent K(2) and two equivalent Ta(2) atoms.
K4BaTa6(Si2O13)2 crystallizes in the orthorhombic Amm2 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 4-coordinate geometry to two equivalent O(5) and two equivalent O(6) atoms. Both K(1)-O(5) bond lengths are 2.85 Å. Both K(1)-O(6) bond lengths are 2.70 Å. In the second K site, K(2) is bonded in a 13-coordinate geometry to one O(2), two equivalent O(3), two equivalent O(4), two equivalent O(6), two equivalent O(8), and four equivalent O(7) atoms. The K(2)-O(2) bond length is 3.22 Å. Both K(2)-O(3) bond lengths are 2.94 Å. Both K(2)-O(4) bond lengths are 3.07 Å. Both K(2)-O(6) bond lengths are 2.94 Å. There is one shorter (3.28 Å) and one longer (3.31 Å) K(2)-O(8) bond length. There are two shorter (2.95 Å) and two longer (3.11 Å) K(2)-O(7) bond lengths. Ba(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(8), four equivalent O(3), and four equivalent O(4) atoms. Both Ba(1)-O(1) bond lengths are 2.90 Å. Both Ba(1)-O(8) bond lengths are 3.14 Å. All Ba(1)-O(3) bond lengths are 3.03 Å. All Ba(1)-O(4) bond lengths are 2.95 Å. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(3), one O(6), one O(7), one O(8), and one O(9) atom to form TaO6 octahedra that share  a cornercorner with one Ta(2)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 3-32°. The Ta(1)-O(1) bond length is 1.96 Å. The Ta(1)-O(3) bond length is 2.06 Å. The Ta(1)-O(6) bond length is 1.97 Å. The Ta(1)-O(7) bond length is 2.05 Å. The Ta(1)-O(8) bond length is 1.98 Å. The Ta(1)-O(9) bond length is 1.98 Å. In the second Ta site, Ta(2) is bonded to one O(10), one O(2), two equivalent O(4), and two equivalent O(6) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 2-32°. The Ta(2)-O(10) bond length is 1.98 Å. The Ta(2)-O(2) bond length is 1.97 Å. Both Ta(2)-O(4) bond lengths are 2.06 Å. Both Ta(2)-O(6) bond lengths are 1.96 Å. Si(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ta(2)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-27°. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(4) bond length is 1.63 Å. The Si(1)-O(5) bond length is 1.64 Å. The Si(1)-O(7) bond length is 1.63 Å. There are ten inequivalent O sites. In the first O site, O(3) is bonded in a distorted bent 150 degrees geometry to one K(2), one Ba(1), one Ta(1), and one Si(1) atom. In the second O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(2), one Ba(1), one Ta(2), and one Si(1) atom. In the third O site, O(5) is bonded in a distorted linear geometry to two equivalent K(1) and two equivalent Si(1) atoms. In the fourth O site, O(6) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Ta(1), and one Ta(2) atom. In the fifth O site, O(7) is bonded in a distorted bent 150 degrees geometry to two equivalent K(2), one Ta(1), and one Si(1) atom. In the sixth O site, O(8) is bonded in a linear geometry to two equivalent K(2), one Ba(1), and two equivalent Ta(1) atoms. In the seventh O site, O(9) is bonded in a distorted linear geometry to two equivalent Ta(1) atoms. In the eighth O site, O(10) is bonded in a distorted linear geometry to two equivalent Ta(2) atoms. In the ninth O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and two equivalent Ta(1) atoms. In the tenth O site, O(2) is bonded in a linear geometry to two equivalent K(2) and two equivalent Ta(2) atoms.