Six-dimensional quantum dynamics for dissociative chemisorption of H2 and D2 on Ag(111) on a permutation invariant potential energy surface

Abstract

A six-dimensional potential energy surface (PES) for H₂ dissociation on rigid Ag(111) is developed by fitting ∼4000 plane-wave density functional theory points using the recently proposed permutation invariant polynomial-neural network (PIP-NN) method, which enforces both the surface periodicity and molecular permutation symmetry. Quantum reactive scattering calculations on the PIP-NN PES yielded dissociative sticking probabilities for both H₂ and D₂. Good agreement with experiment was achieved at high collision energies, but the agreement is less satisfactory at low collision energies, due apparently to the neglect of surface temperature in our model. The dissociation is activated by both vibrational and translational excitations, with roughly equal efficacies. Rotational and alignment effects were examined and found to be quite similar to hydrogen dissociation on Ag(100) and Cu(111).