Dissociation of N-2 on chromium alloys: A general mechanism for dissociation of diatomic molecules

In this work we use ab initio Hartree-Fock effective core potentials to ana lyze N-2 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 i nclined state is energetically more favorable than the perpendicular config uration. In comparison with monometallic surfaces, some of the bimetallic s ystems, such as Cr4ScN2, Cr4TiN2, and Cr3V2N2, are found to have larger N-N distances, surface-->N-2 charge transfers, higher Fermi energies, and smal ler N-N stretching frequencies, indicating greater efficiency of these allo ys for dissociation. The theoretical parameters obtained from these bimetal lic catalytic systems are interpreted using a general mechanism proposed fo r dissociation of diatomic molecules on transition metal surfaces. [S0163-1 829(99)02639-9].