Nb3B4 crystallizes in the orthorhombic Immm space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 7-coordinate geometry to two equivalent B(1) and five equivalent B(2) atoms. In the second Nb site, Nb(2) is bonded to four equivalent B(2) and eight equivalent B(1) atoms to form a mixture of face and edge-sharing NbB12 cuboctahedra. There are two inequivalent B sites. In the first B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Nb(2), five equivalent Nb(1), and two equivalent B(1) atoms. In the second B site, B(1) is bonded in a 9-coordinate geometry to two equivalent Nb(1), four equivalent Nb(2), one B(1), and two equivalent B(2) atoms.
Nb3B4 crystallizes in the orthorhombic Immm space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 7-coordinate geometry to two equivalent B(1) and five equivalent B(2) atoms. Both Nb(1)-B(1) bond lengths are 2.38 Å. There are four shorter (2.41 Å) and one longer (2.59 Å) Nb(1)-B(2) bond length. In the second Nb site, Nb(2) is bonded to four equivalent B(2) and eight equivalent B(1) atoms to form a mixture of face and edge-sharing NbB12 cuboctahedra. All Nb(2)-B(2) bond lengths are 2.50 Å. All Nb(2)-B(1) bond lengths are 2.46 Å. There are two inequivalent B sites. In the first B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Nb(2), five equivalent Nb(1), and two equivalent B(1) atoms. Both B(2)-B(1) bond lengths are 1.85 Å. In the second B site, B(1) is bonded in a 9-coordinate geometry to two equivalent Nb(1), four equivalent Nb(2), one B(1), and two equivalent B(2) atoms. The B(1)-B(1) bond length is 1.82 Å.