SiB3 crystallizes in the orthorhombic Imma space group. There are four inequivalent B sites. In the first B site, B(1) is bonded in a 6-coordinate geometry to one B(4), two equivalent B(2), two equivalent B(3), and one Si(2) atom. In the second B site, B(2) is bonded in a 6-coordinate geometry to one B(1), one B(2), one B(4), two equivalent B(3), and one Si(1) atom. In the third B site, B(3) is bonded in a 6-coordinate geometry to one B(1), one B(4), two equivalent B(2), and two equivalent B(3) atoms. In the fourth B site, B(4) is bonded in a 6-coordinate geometry to one B(1), two equivalent B(2), two equivalent B(3), and one Si(2) atom. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 5-coordinate geometry to two equivalent B(2), one Si(1), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a distorted bent 120 degrees geometry to one B(1), one B(4), and two equivalent Si(1) atoms.
SiB3 crystallizes in the orthorhombic Imma space group. There are four inequivalent B sites. In the first B site, B(1) is bonded in a 6-coordinate geometry to one B(4), two equivalent B(2), two equivalent B(3), and one Si(2) atom. The B(1)-B(4) bond length is 1.80 Å. Both B(1)-B(2) bond lengths are 1.75 Å. Both B(1)-B(3) bond lengths are 1.78 Å. The B(1)-Si(2) bond length is 1.97 Å. In the second B site, B(2) is bonded in a 6-coordinate geometry to one B(1), one B(2), one B(4), two equivalent B(3), and one Si(1) atom. The B(2)-B(2) bond length is 1.85 Å. The B(2)-B(4) bond length is 1.77 Å. There is one shorter (1.79 Å) and one longer (1.80 Å) B(2)-B(3) bond length. The B(2)-Si(1) bond length is 2.03 Å. In the third B site, B(3) is bonded in a 6-coordinate geometry to one B(1), one B(4), two equivalent B(2), and two equivalent B(3) atoms. The B(3)-B(4) bond length is 1.77 Å. There is one shorter (1.72 Å) and one longer (1.93 Å) B(3)-B(3) bond length. In the fourth B site, B(4) is bonded in a 6-coordinate geometry to one B(1), two equivalent B(2), two equivalent B(3), and one Si(2) atom. The B(4)-Si(2) bond length is 2.01 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 5-coordinate geometry to two equivalent B(2), one Si(1), and two equivalent Si(2) atoms. The Si(1)-Si(1) bond length is 2.33 Å. Both Si(1)-Si(2) bond lengths are 2.58 Å. In the second Si site, Si(2) is bonded in a distorted bent 120 degrees geometry to one B(1), one B(4), and two equivalent Si(1) atoms.