B4C crystallizes in the trigonal R-3m space group. There are two inequivalent B sites. In the first B site, B(1) is bonded in a single-bond geometry to two equivalent B(2) and one C(1) atom. In the second B site, B(2) is bonded in a 4-coordinate geometry to two equivalent B(1) and two equivalent B(2) atoms. There are two inequivalent C sites. In the first C site, C(2) is bonded in a linear geometry to two equivalent C(1) atoms. In the second C site, C(1) is bonded to three equivalent B(1) and one C(2) atom to form distorted corner-sharing CB3C tetrahedra.
B4C crystallizes in the trigonal R-3m space group. There are two inequivalent B sites. In the first B site, B(1) is bonded in a single-bond geometry to two equivalent B(2) and one C(1) atom. There is one shorter (1.57 Å) and one longer (1.90 Å) B(1)-B(2) bond length. The B(1)-C(1) bond length is 1.61 Å. In the second B site, B(2) is bonded in a 4-coordinate geometry to two equivalent B(1) and two equivalent B(2) atoms. Both B(2)-B(2) bond lengths are 1.65 Å. There are two inequivalent C sites. In the first C site, C(2) is bonded in a linear geometry to two equivalent C(1) atoms. Both C(2)-C(1) bond lengths are 1.38 Å. In the second C site, C(1) is bonded to three equivalent B(1) and one C(2) atom to form distorted corner-sharing CB3C tetrahedra.