Gd2B4O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a 10-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(7), one O(8), two equivalent O(1), and two equivalent O(9) atoms. In the second Gd site, Gd(2) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), two equivalent O(3), and two equivalent O(8) atoms. There are four inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(4), one O(7), and one O(8) atom. In the second B site, B(2) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form corner-sharing BO4 tetrahedra. In the third B site, B(3) is bonded to one O(2), one O(4), one O(6), and one O(9) atom to form corner-sharing BO4 tetrahedra. In the fourth B site, B(4) is bonded to one O(5), one O(6), one O(7), and one O(9) atom to form corner-sharing BO4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Gd(2), two equivalent Gd(1), and one B(2) atom to form distorted edge-sharing OGd3B tetrahedra. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Gd(1), one Gd(2), one B(2), and one B(3) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Gd(1), two equivalent Gd(2), and one B(2) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Gd(1), one Gd(2), one B(1), and one B(3) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Gd(1), one Gd(2), one B(2), and one B(4) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Gd(2), one B(3), and one B(4) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Gd(1), one B(1), and one B(4) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Gd(1), two equivalent Gd(2), and one B(1) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to two equivalent Gd(1), one B(3), and one B(4) atom.
Gd2B4O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a 10-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(7), one O(8), two equivalent O(1), and two equivalent O(9) atoms. The Gd(1)-O(2) bond length is 2.55 Å. The Gd(1)-O(3) bond length is 2.45 Å. The Gd(1)-O(4) bond length is 2.55 Å. The Gd(1)-O(5) bond length is 2.63 Å. The Gd(1)-O(7) bond length is 2.51 Å. The Gd(1)-O(8) bond length is 2.46 Å. There is one shorter (2.29 Å) and one longer (2.37 Å) Gd(1)-O(1) bond length. There is one shorter (2.43 Å) and one longer (2.56 Å) Gd(1)-O(9) bond length. In the second Gd site, Gd(2) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), two equivalent O(3), and two equivalent O(8) atoms. The Gd(2)-O(1) bond length is 2.38 Å. The Gd(2)-O(2) bond length is 2.56 Å. The Gd(2)-O(4) bond length is 2.69 Å. The Gd(2)-O(5) bond length is 2.64 Å. The Gd(2)-O(6) bond length is 2.33 Å. There is one shorter (2.36 Å) and one longer (2.39 Å) Gd(2)-O(3) bond length. There is one shorter (2.42 Å) and one longer (2.59 Å) Gd(2)-O(8) bond length. There are four inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(4), one O(7), and one O(8) atom. The B(1)-O(4) bond length is 1.39 Å. The B(1)-O(7) bond length is 1.36 Å. The B(1)-O(8) bond length is 1.36 Å. In the second B site, B(2) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form corner-sharing BO4 tetrahedra. The B(2)-O(1) bond length is 1.47 Å. The B(2)-O(2) bond length is 1.55 Å. The B(2)-O(3) bond length is 1.46 Å. The B(2)-O(5) bond length is 1.46 Å. In the third B site, B(3) is bonded to one O(2), one O(4), one O(6), and one O(9) atom to form corner-sharing BO4 tetrahedra. The B(3)-O(2) bond length is 1.46 Å. The B(3)-O(4) bond length is 1.50 Å. The B(3)-O(6) bond length is 1.44 Å. The B(3)-O(9) bond length is 1.50 Å. In the fourth B site, B(4) is bonded to one O(5), one O(6), one O(7), and one O(9) atom to form corner-sharing BO4 tetrahedra. The B(4)-O(5) bond length is 1.46 Å. The B(4)-O(6) bond length is 1.42 Å. The B(4)-O(7) bond length is 1.48 Å. The B(4)-O(9) bond length is 1.47 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Gd(2), two equivalent Gd(1), and one B(2) atom to form distorted edge-sharing OGd3B tetrahedra. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Gd(1), one Gd(2), one B(2), and one B(3) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Gd(1), two equivalent Gd(2), and one B(2) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Gd(1), one Gd(2), one B(1), and one B(3) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Gd(1), one Gd(2), one B(2), and one B(4) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Gd(2), one B(3), and one B(4) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Gd(1), one B(1), and one B(4) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Gd(1), two equivalent Gd(2), and one B(1) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to two equivalent Gd(1), one B(3), and one B(4) atom.