Quantum and thermal effects inH2dissociative adsorption: Evaluation of free energy barriers in multidimensional quantum systems

We have evaluated the sticking probability and activation energy for dissociation of ${\mathrm{H}}_2$ molecules on a Cu(110) surface by a reversible work formulation of quantum transition state theory. Feynman path integrals are used to describe the two hydrogen atoms and a few of the surface atoms, thereby including quantum effects such as tunneling and zero point energy, as well as thermal averaging. At a temperature below 600 K an onset of a quantum regime is observed as the activation energy drops by 30%.