Reactive and diffractive scattering of H2 from Pt(111) studied using a six-dimensional wave packet method

Abstract

We present results of calculations on dissociative and rotationally (in)elastic diffractive scattering of H2 from Pt(111), treating all six molecular degrees of freedom quantum mechanically. The six-dimensional (6D) potential energy surface was taken from density functional theory calculations using the generalized gradient approximation and a slab representation of the metal surface. The 6D calculations show that out-of-plane diffraction is very efficient, at the cost of in-plane diffraction, as was the case in previous four-dimensional (4D) calculations. This could explain why so little in-plane diffraction was found in scattering experiments, suggesting the surface to be flat, whereas experiments on reaction suggested a corrugated surface. Results of calculations for off-normal incidence of (v=0,j=0) H2 show that initial parallel momentum inhibits dissociation at low normal translational energies, in agreement with experiment, but has little effect for higher energies. Reaction of initial (v=1,j=0) H2 is predicted to be vibrationally enhanced with respect to (v=0,j=0) H2, as was also found in three-dimensional (3D) and 4D calculations, even though H2+Pt(111) is an early barrier system.