Potential energy surfaces for the reaction Al+O-2 -> AlO+O

Abstract

Potential energy surfaces for the reaction Al + O-2 --> AlO + O have been calculated with the multireference configuration interaction (MRCI) method using molecular orbitals derived from the complete active space self-consistent field (CASSCF) calculations. The end-on geometry is the most favourable for the reaction to take place. The small reaction barrier in the present calculation (0.11 eV) is probably an artefact related to the ionic-neutral avoided crossing. The charge analysis implies that the title oxidation reaction occurs through a harpooning mechanism. Along the potential energy surface of the reaction, there are two stable intermediates of AlO2 (C-infinityv and C-2v) at least 2.74 eV below the energy of reactants. The calculated enthalpy of the reaction (-0.07 eV) is in excellent agreement with the experimental value (-0.155 eV) in part due to the fortuitous cancellation of errors in AlO and O-2 calculations.