Ga4B2O9 crystallizes in the monoclinic Cm space group. There are six inequivalent Ga sites. In the first Ga site, Ga(1) is bonded to one O(1), one O(11), one O(12), one O(2), one O(5), and one O(6) atom to form GaO6 octahedra that share  a cornercorner with one Ga(3)O4 tetrahedra,  a cornercorner with one Ga(6)O4 tetrahedra,  a cornercorner with one B(4)O4 tetrahedra,  a cornercorner with one Ga(5)O5 trigonal bipyramid, edges with two equivalent Ga(1)O6 octahedra, and  an edgeedge with one Ga(2)O5 trigonal bipyramid. In the second Ga site, Ga(2) is bonded to one O(11), one O(13), one O(3), and two equivalent O(1) atoms to form GaO5 trigonal bipyramids that share corners with two equivalent Ga(4)O6 octahedra,  a cornercorner with one Ga(3)O4 tetrahedra,  a cornercorner with one Ga(6)O4 tetrahedra, edges with two equivalent Ga(1)O6 octahedra, and  an edgeedge with one Ga(5)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 48°. In the third Ga site, Ga(3) is bonded to one O(13), one O(4), and two equivalent O(2) atoms to form distorted GaO4 tetrahedra that share corners with two equivalent Ga(1)O6 octahedra, corners with two equivalent Ga(4)O6 octahedra, corners with two equivalent B(4)O4 tetrahedra,  a cornercorner with one Ga(2)O5 trigonal bipyramid, and  a cornercorner with one Ga(5)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 52-76°. In the fourth Ga site, Ga(4) is bonded to one O(10), one O(3), one O(4), one O(7), one O(8), and one O(9) atom to form GaO6 octahedra that share  a cornercorner with one Ga(3)O4 tetrahedra,  a cornercorner with one Ga(6)O4 tetrahedra,  a cornercorner with one B(4)O4 tetrahedra,  a cornercorner with one Ga(2)O5 trigonal bipyramid, edges with two equivalent Ga(4)O6 octahedra, and  an edgeedge with one Ga(5)O5 trigonal bipyramid. In the fifth Ga site, Ga(5) is bonded to one O(12), one O(13), one O(3), and two equivalent O(8) atoms to form GaO5 trigonal bipyramids that share corners with two equivalent Ga(1)O6 octahedra,  a cornercorner with one Ga(3)O4 tetrahedra, edges with two equivalent Ga(4)O6 octahedra, and  an edgeedge with one Ga(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 51°. In the sixth Ga site, Ga(6) is bonded to one O(11), one O(14), and two equivalent O(7) atoms to form GaO4 tetrahedra that share corners with two equivalent Ga(1)O6 octahedra, corners with two equivalent Ga(4)O6 octahedra,  a cornercorner with one B(4)O4 tetrahedra, and  a cornercorner with one Ga(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 70°. There are four inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(7) atoms. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(6) and two equivalent O(8) atoms. In the third B site, B(3) is bonded in a trigonal planar geometry to one O(9) and two equivalent O(1) atoms. In the fourth B site, B(4) is bonded to one O(10), one O(14), and two equivalent O(2) atoms to form BO4 tetrahedra that share corners with two equivalent Ga(1)O6 octahedra, corners with two equivalent Ga(4)O6 octahedra,  a cornercorner with one Ga(6)O4 tetrahedra, and corners with two equivalent Ga(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-58°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ga(1), one Ga(2), and one B(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ga(1), one Ga(3), and one B(4) atom. In the third O site, O(3) is bonded in a trigonal pyramidal geometry to one Ga(2), one Ga(5), and two equivalent Ga(4) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Ga(3) and two equivalent Ga(4) atoms. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to two equivalent Ga(1) and one B(1) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to two equivalent Ga(1) and one B(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Ga(4), one Ga(6), and one B(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Ga(4), one Ga(5), and one B(2) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to two equivalent Ga(4) and one B(3) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to two equivalent Ga(4) and one B(4) atom. In the eleventh O site, O(11) is bonded in a distorted rectangular see-saw-like geometry to one Ga(2), one Ga(6), and two equivalent Ga(1) atoms. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Ga(5) and two equivalent Ga(1) atoms. In the thirteenth O site, O(13) is bonded in a distorted T-shaped geometry to one Ga(2), one Ga(3), and one Ga(5) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one Ga(6) and one B(4) atom.
Ga4B2O9 crystallizes in the monoclinic Cm space group. There are six inequivalent Ga sites. In the first Ga site, Ga(1) is bonded to one O(1), one O(11), one O(12), one O(2), one O(5), and one O(6) atom to form GaO6 octahedra that share  a cornercorner with one Ga(3)O4 tetrahedra,  a cornercorner with one Ga(6)O4 tetrahedra,  a cornercorner with one B(4)O4 tetrahedra,  a cornercorner with one Ga(5)O5 trigonal bipyramid, edges with two equivalent Ga(1)O6 octahedra, and  an edgeedge with one Ga(2)O5 trigonal bipyramid. The Ga(1)-O(1) bond length is 2.05 Å. The Ga(1)-O(11) bond length is 1.94 Å. The Ga(1)-O(12) bond length is 1.86 Å. The Ga(1)-O(2) bond length is 1.94 Å. The Ga(1)-O(5) bond length is 2.03 Å. The Ga(1)-O(6) bond length is 2.00 Å. In the second Ga site, Ga(2) is bonded to one O(11), one O(13), one O(3), and two equivalent O(1) atoms to form GaO5 trigonal bipyramids that share corners with two equivalent Ga(4)O6 octahedra,  a cornercorner with one Ga(3)O4 tetrahedra,  a cornercorner with one Ga(6)O4 tetrahedra, edges with two equivalent Ga(1)O6 octahedra, and  an edgeedge with one Ga(5)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 48°. The Ga(2)-O(11) bond length is 2.07 Å. The Ga(2)-O(13) bond length is 1.85 Å. The Ga(2)-O(3) bond length is 1.94 Å. Both Ga(2)-O(1) bond lengths are 1.90 Å. In the third Ga site, Ga(3) is bonded to one O(13), one O(4), and two equivalent O(2) atoms to form distorted GaO4 tetrahedra that share corners with two equivalent Ga(1)O6 octahedra, corners with two equivalent Ga(4)O6 octahedra, corners with two equivalent B(4)O4 tetrahedra,  a cornercorner with one Ga(2)O5 trigonal bipyramid, and  a cornercorner with one Ga(5)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 52-76°. The Ga(3)-O(13) bond length is 1.87 Å. The Ga(3)-O(4) bond length is 1.81 Å. Both Ga(3)-O(2) bond lengths are 1.88 Å. In the fourth Ga site, Ga(4) is bonded to one O(10), one O(3), one O(4), one O(7), one O(8), and one O(9) atom to form GaO6 octahedra that share  a cornercorner with one Ga(3)O4 tetrahedra,  a cornercorner with one Ga(6)O4 tetrahedra,  a cornercorner with one B(4)O4 tetrahedra,  a cornercorner with one Ga(2)O5 trigonal bipyramid, edges with two equivalent Ga(4)O6 octahedra, and  an edgeedge with one Ga(5)O5 trigonal bipyramid. The Ga(4)-O(10) bond length is 1.94 Å. The Ga(4)-O(3) bond length is 1.93 Å. The Ga(4)-O(4) bond length is 1.86 Å. The Ga(4)-O(7) bond length is 2.03 Å. The Ga(4)-O(8) bond length is 2.06 Å. The Ga(4)-O(9) bond length is 2.03 Å. In the fifth Ga site, Ga(5) is bonded to one O(12), one O(13), one O(3), and two equivalent O(8) atoms to form GaO5 trigonal bipyramids that share corners with two equivalent Ga(1)O6 octahedra,  a cornercorner with one Ga(3)O4 tetrahedra, edges with two equivalent Ga(4)O6 octahedra, and  an edgeedge with one Ga(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 51°. The Ga(5)-O(12) bond length is 1.83 Å. The Ga(5)-O(13) bond length is 1.92 Å. The Ga(5)-O(3) bond length is 2.05 Å. Both Ga(5)-O(8) bond lengths are 1.89 Å. In the sixth Ga site, Ga(6) is bonded to one O(11), one O(14), and two equivalent O(7) atoms to form GaO4 tetrahedra that share corners with two equivalent Ga(1)O6 octahedra, corners with two equivalent Ga(4)O6 octahedra,  a cornercorner with one B(4)O4 tetrahedra, and  a cornercorner with one Ga(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 70°. The Ga(6)-O(11) bond length is 1.92 Å. The Ga(6)-O(14) bond length is 1.79 Å. Both Ga(6)-O(7) bond lengths are 1.90 Å. There are four inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(7) atoms. The B(1)-O(5) bond length is 1.35 Å. Both B(1)-O(7) bond lengths are 1.39 Å. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(6) and two equivalent O(8) atoms. The B(2)-O(6) bond length is 1.37 Å. Both B(2)-O(8) bond lengths are 1.38 Å. In the third B site, B(3) is bonded in a trigonal planar geometry to one O(9) and two equivalent O(1) atoms. The B(3)-O(9) bond length is 1.37 Å. Both B(3)-O(1) bond lengths are 1.38 Å. In the fourth B site, B(4) is bonded to one O(10), one O(14), and two equivalent O(2) atoms to form BO4 tetrahedra that share corners with two equivalent Ga(1)O6 octahedra, corners with two equivalent Ga(4)O6 octahedra,  a cornercorner with one Ga(6)O4 tetrahedra, and corners with two equivalent Ga(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-58°. The B(4)-O(10) bond length is 1.48 Å. The B(4)-O(14) bond length is 1.44 Å. Both B(4)-O(2) bond lengths are 1.54 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ga(1), one Ga(2), and one B(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ga(1), one Ga(3), and one B(4) atom. In the third O site, O(3) is bonded in a trigonal pyramidal geometry to one Ga(2), one Ga(5), and two equivalent Ga(4) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Ga(3) and two equivalent Ga(4) atoms. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to two equivalent Ga(1) and one B(1) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to two equivalent Ga(1) and one B(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Ga(4), one Ga(6), and one B(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Ga(4), one Ga(5), and one B(2) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to two equivalent Ga(4) and one B(3) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to two equivalent Ga(4) and one B(4) atom. In the eleventh O site, O(11) is bonded in a distorted rectangular see-saw-like geometry to one Ga(2), one Ga(6), and two equivalent Ga(1) atoms. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Ga(5) and two equivalent Ga(1) atoms. In the thirteenth O site, O(13) is bonded in a distorted T-shaped geometry to one Ga(2), one Ga(3), and one Ga(5) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one Ga(6) and one B(4) atom.