BaGe3O8 crystallizes in the monoclinic C2/c space group. Ba(1) is bonded to two equivalent O(1), two equivalent O(3), four equivalent O(2), and four equivalent O(4) atoms to form BaO12 cuboctahedra that share corners with two equivalent Ge(2)O6 octahedra, corners with four equivalent Ge(1)O6 octahedra, edges with four equivalent Ba(1)O12 cuboctahedra, edges with two equivalent Ge(1)O6 octahedra, edges with four equivalent Ge(2)O6 octahedra, and faces with two equivalent Ge(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-47°. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form GeO6 octahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, corners with two equivalent Ge(2)O6 octahedra, edges with two equivalent Ba(1)O12 cuboctahedra, and edges with four equivalent Ge(2)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. In the second Ge site, Ge(2) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form GeO6 octahedra that share  a cornercorner with one Ba(1)O12 cuboctahedra,  a cornercorner with one Ge(1)O6 octahedra, corners with two equivalent Ge(2)O6 octahedra, edges with two equivalent Ba(1)O12 cuboctahedra,  an edgeedge with one Ge(2)O6 octahedra, edges with two equivalent Ge(1)O6 octahedra, and  a faceface with one Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 49-54°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ba(1), one Ge(1), and two equivalent Ge(2) atoms. In the second O site, O(2) is bonded in a distorted water-like geometry to two equivalent Ba(1), one Ge(1), and one Ge(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), one Ge(1), and two equivalent Ge(2) atoms. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one Ge(2) atom.
BaGe3O8 crystallizes in the monoclinic C2/c space group. Ba(1) is bonded to two equivalent O(1), two equivalent O(3), four equivalent O(2), and four equivalent O(4) atoms to form BaO12 cuboctahedra that share corners with two equivalent Ge(2)O6 octahedra, corners with four equivalent Ge(1)O6 octahedra, edges with four equivalent Ba(1)O12 cuboctahedra, edges with two equivalent Ge(1)O6 octahedra, edges with four equivalent Ge(2)O6 octahedra, and faces with two equivalent Ge(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-47°. Both Ba(1)-O(1) bond lengths are 3.13 Å. Both Ba(1)-O(3) bond lengths are 2.88 Å. There are two shorter (2.95 Å) and two longer (3.07 Å) Ba(1)-O(2) bond lengths. There are two shorter (2.88 Å) and two longer (2.92 Å) Ba(1)-O(4) bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form GeO6 octahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, corners with two equivalent Ge(2)O6 octahedra, edges with two equivalent Ba(1)O12 cuboctahedra, and edges with four equivalent Ge(2)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. Both Ge(1)-O(1) bond lengths are 1.97 Å. Both Ge(1)-O(2) bond lengths are 1.89 Å. Both Ge(1)-O(3) bond lengths are 1.93 Å. In the second Ge site, Ge(2) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form GeO6 octahedra that share  a cornercorner with one Ba(1)O12 cuboctahedra,  a cornercorner with one Ge(1)O6 octahedra, corners with two equivalent Ge(2)O6 octahedra, edges with two equivalent Ba(1)O12 cuboctahedra,  an edgeedge with one Ge(2)O6 octahedra, edges with two equivalent Ge(1)O6 octahedra, and  a faceface with one Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 49-54°. The Ge(2)-O(2) bond length is 1.86 Å. The Ge(2)-O(4) bond length is 1.85 Å. There is one shorter (1.92 Å) and one longer (1.95 Å) Ge(2)-O(1) bond length. There is one shorter (1.99 Å) and one longer (2.03 Å) Ge(2)-O(3) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ba(1), one Ge(1), and two equivalent Ge(2) atoms. In the second O site, O(2) is bonded in a distorted water-like geometry to two equivalent Ba(1), one Ge(1), and one Ge(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), one Ge(1), and two equivalent Ge(2) atoms. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one Ge(2) atom.