Ba2Ge5Si3O18 crystallizes in the hexagonal P-6 space group. Ba(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form GeO6 octahedra that share corners with three equivalent Ge(2)O4 tetrahedra and corners with three equivalent Si(1)O4 tetrahedra. In the second Ge site, Ge(2) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form GeO4 tetrahedra that share corners with two equivalent Ge(1)O6 octahedra and corners with two equivalent Ge(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. Si(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with two equivalent Ge(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ba(1), one Ge(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ba(1), one Ge(1), and one Ge(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to two equivalent Si(1) atoms. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Ge(2) atoms.
Ba2Ge5Si3O18 crystallizes in the hexagonal P-6 space group. Ba(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. All Ba(1)-O(1) bond lengths are 2.87 Å. All Ba(1)-O(2) bond lengths are 2.76 Å. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form GeO6 octahedra that share corners with three equivalent Ge(2)O4 tetrahedra and corners with three equivalent Si(1)O4 tetrahedra. All Ge(1)-O(1) bond lengths are 1.90 Å. All Ge(1)-O(2) bond lengths are 1.91 Å. In the second Ge site, Ge(2) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form GeO4 tetrahedra that share corners with two equivalent Ge(1)O6 octahedra and corners with two equivalent Ge(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. Both Ge(2)-O(2) bond lengths are 1.75 Å. There is one shorter (1.77 Å) and one longer (1.80 Å) Ge(2)-O(4) bond length. Si(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with two equivalent Ge(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. Both Si(1)-O(1) bond lengths are 1.62 Å. There is one shorter (1.66 Å) and one longer (1.67 Å) Si(1)-O(3) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ba(1), one Ge(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ba(1), one Ge(1), and one Ge(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to two equivalent Si(1) atoms. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Ge(2) atoms.