BaCuSi2O6 crystallizes in the tetragonal I4_1/a space group. Ba(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(6) atoms. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Si(1), and one Si(2) atom. In the second O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(2), and one Si(1) atom. In the third O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(1), and one Si(2) atom. In the fourth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(1), and one Si(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Si(1), and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(2), and one Si(1) atom.
BaCuSi2O6 crystallizes in the tetragonal I4_1/a space group. Ba(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. There is one shorter (3.19 Å) and one longer (3.33 Å) Ba(1)-O(1) bond length. There is one shorter (2.93 Å) and one longer (2.97 Å) Ba(1)-O(2) bond length. There is one shorter (3.17 Å) and one longer (3.35 Å) Ba(1)-O(3) bond length. There is one shorter (2.93 Å) and one longer (2.98 Å) Ba(1)-O(4) bond length. There is one shorter (2.94 Å) and one longer (2.97 Å) Ba(1)-O(5) bond length. There is one shorter (2.94 Å) and one longer (2.97 Å) Ba(1)-O(6) bond length. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(6) atoms. Both Cu(1)-O(2) bond lengths are 1.96 Å. Both Cu(1)-O(6) bond lengths are 1.96 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. Both Cu(2)-O(4) bond lengths are 1.95 Å. Both Cu(2)-O(5) bond lengths are 1.95 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.65 Å. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.62 Å. The Si(1)-O(5) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(1) bond length is 1.65 Å. The Si(2)-O(2) bond length is 1.62 Å. The Si(2)-O(3) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.63 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Si(1), and one Si(2) atom. In the second O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(2), and one Si(1) atom. In the third O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(1), and one Si(2) atom. In the fourth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(1), and one Si(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Si(1), and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(2), and one Si(1) atom.