Dissociation of N2 on chromium alloys: A general mechanism for dissociation of diatomic molecules

In this work we use ab initio Hartree-Fock effective core potentials to analyze N₂ dissociation on doped (bimetallic) Cr (110) surfaces described by Cr₄MN₂ and Cr₃M₂N₂ (M=Sc, Ti, V, Fe, Co, Ni, Zn, Mg, Ca) clusters in both perpendicular and inclined configurations. Our results indicate that the inclined state is energetically more favorable than the perpendicular configuration. In comparison with monometallic surfaces, some of the bimetallic systems, such as Cr₄ScN₂, Cr₄TiN₂, and Cr₃V₂N₂, are found to have larger N-N distances, surface-->N₂ charge transfers, higher Fermi energies, and smaller N-N stretching frequencies, indicating greater efficiency of these alloys for dissociation. The theoretical parameters obtained from these bimetallic catalytic systems are interpreted using a general mechanism proposed for dissociation of diatomic molecules on transition metal surfaces.