BaZrSi3O9 crystallizes in the hexagonal P-6c2 space group. Ba(1) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. Zr(1) is bonded to six equivalent O(1) atoms to form ZrO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Si(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with two equivalent Zr(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ba(1), one Zr(1), and one Si(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to two equivalent Si(1) atoms.
BaZrSi3O9 crystallizes in the hexagonal P-6c2 space group. Ba(1) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. All Ba(1)-O(1) bond lengths are 2.83 Å. Zr(1) is bonded to six equivalent O(1) atoms to form ZrO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. All Zr(1)-O(1) bond lengths are 2.11 Å. Si(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with two equivalent Zr(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. Both Si(1)-O(1) bond lengths are 1.63 Å. There is one shorter (1.65 Å) and one longer (1.66 Å) Si(1)-O(2) bond length. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ba(1), one Zr(1), and one Si(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to two equivalent Si(1) atoms.