Ba3Si4Ta6O26 crystallizes in the hexagonal P-62m space group. Ba(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(5), and eight equivalent O(2) atoms. Ta(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(5) 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 5-33°. Si(1) is bonded to one O(3) 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 31°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Ba(1) and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Ta(1), and one Si(1) atom. In the third O site, O(3) is bonded in a linear geometry to two equivalent Si(1) atoms. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Ta(1) atoms. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and two equivalent Ta(1) atoms.
Ba3Si4Ta6O26 crystallizes in the hexagonal P-62m space group. Ba(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(5), and eight equivalent O(2) atoms. Both Ba(1)-O(1) bond lengths are 3.12 Å. Both Ba(1)-O(5) bond lengths are 2.87 Å. There are four shorter (2.88 Å) and four longer (2.97 Å) Ba(1)-O(2) bond lengths. Ta(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(5) 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 5-33°. The Ta(1)-O(1) bond length is 1.99 Å. The Ta(1)-O(4) bond length is 1.93 Å. Both Ta(1)-O(2) bond lengths are 2.05 Å. Both Ta(1)-O(5) bond lengths are 1.94 Å. Si(1) is bonded to one O(3) 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 31°. The Si(1)-O(3) bond length is 1.60 Å. All Si(1)-O(2) bond lengths are 1.62 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Ba(1) and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Ta(1), and one Si(1) atom. In the third O site, O(3) is bonded in a linear geometry to two equivalent Si(1) atoms. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Ta(1) atoms. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and two equivalent Ta(1) atoms.