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Nb2C is trigonal omega structured and crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one Nb2C sheet oriented in the (0, 0, 1) direction. Nb2+ is bonded in a distorted T-shaped geometry to three equivalent C4- atoms. All Nb–C bond lengths are 2.21 Å. C4- is bonded to six equivalent Nb2+ atoms to form edge-sharing CNb6 octahedra.
Nb2C is beta Vanadium nitride-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Nb2+ sites. In the first Nb2+ site, Nb2+ is bonded in a distorted T-shaped geometry to three equivalent C4- atoms. There are two shorter (2.19 Å) and one longer (2.25 Å) Nb–C bond lengths. In the second Nb2+ site, Nb2+ is bonded in a distorted T-shaped geometry to three equivalent C4- atoms. There are two shorter (2.19 Å) and one longer (2.22 Å) Nb–C bond lengths. C4- is bonded to six Nb2+ atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles are 50°.