Ba3Si4Ta6O23 crystallizes in the hexagonal P-62m space group. Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(1) and eight equivalent O(2) atoms. Ta(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form TaO5 square pyramids that share corners with three equivalent Ta(1)O5 square pyramids and corners with two equivalent Si(1)O4 tetrahedra. 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)O5 square pyramids and  a cornercorner with one Si(1)O4 tetrahedra. There are four inequivalent O sites. In the first 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 second O site, O(2) is bonded in a 2-coordinate 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 bent 150 degrees geometry to two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Si(1) atoms.
Ba3Si4Ta6O23 crystallizes in the hexagonal P-62m space group. Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(1) and eight equivalent O(2) atoms. Both Ba(1)-O(1) bond lengths are 2.82 Å. There are four shorter (2.85 Å) and four longer (2.95 Å) Ba(1)-O(2) bond lengths. Ta(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form TaO5 square pyramids that share corners with three equivalent Ta(1)O5 square pyramids and corners with two equivalent Si(1)O4 tetrahedra. The Ta(1)-O(3) bond length is 1.95 Å. Both Ta(1)-O(1) bond lengths are 1.95 Å. Both Ta(1)-O(2) bond lengths are 2.06 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)O5 square pyramids and  a cornercorner with one Si(1)O4 tetrahedra. The Si(1)-O(4) bond length is 1.61 Å. All Si(1)-O(2) bond lengths are 1.64 Å. There are four inequivalent O sites. In the first 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 second O site, O(2) is bonded in a 2-coordinate 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 bent 150 degrees geometry to two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Si(1) atoms.