Fe3B crystallizes in the tetragonal I-4 space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 2-coordinate geometry to two equivalent B(1) atoms. In the second Fe site, Fe(3) is bonded in a 3-coordinate geometry to three equivalent B(1) atoms. In the third Fe site, Fe(2) is bonded in a 4-coordinate geometry to four equivalent B(1) atoms. B(1) is bonded in a 9-coordinate geometry to two equivalent Fe(1), three equivalent Fe(3), and four equivalent Fe(2) atoms.
Fe3B crystallizes in the tetragonal I-4 space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 2-coordinate geometry to two equivalent B(1) atoms. There is one shorter (2.13 Å) and one longer (2.23 Å) Fe(1)-B(1) bond length. In the second Fe site, Fe(3) is bonded in a 3-coordinate geometry to three equivalent B(1) atoms. There are a spread of Fe(3)-B(1) bond distances ranging from 2.12-2.31 Å. In the third Fe site, Fe(2) is bonded in a 4-coordinate geometry to four equivalent B(1) atoms. There are a spread of Fe(2)-B(1) bond distances ranging from 2.18-2.21 Å. B(1) is bonded in a 9-coordinate geometry to two equivalent Fe(1), three equivalent Fe(3), and four equivalent Fe(2) atoms.