A practical quasi-classical trajectory method to avoid zero-point energy leakage in dissociative chemisorption of polyatomic molecules on surfaces

Abstract

An accurate prediction of dissociative sticking probabilities (S0) of polyatomic molecules on surfaces has long been a challenging task, because a fully coupled quantum mechanical treatment of numerous degrees of freedom is computationally forbidden. While a quasi-classical trajectory (QCT) approach is much more effective, it often suffers from the leakage of vibrational zero-point energy of the polyatomic molecule, leading to significant and, moreover, initial-state-dependent overestimation of S0 at low incidence energies. Here, inspired by the most frequently used QCT implementation in gas-phase reactions, we propose applying Gaussian binning (GB) instead of standard histogram binning for both scattered and adsorbed species to calculate S0 by the weighted population of trajectories. This new recipe, coupled with two different initial sampling conditions, is tested against the fully coupled quantum dynamical method in D2O dissociation on a rigid Ni(111) surface. We find direct evidence of zero-point energy leakage, rendering the energy in the O–D vibration of the dissociated OD* adsorbate much smaller than its zero-point energy, while GB largely avoids the influence of this artifact on the reactivity. The corrected QCT reaction probabilities thus yield much better agreement with quantum ones than standard QCT results. Impressively, similar improvements are achieved for D2O in both the vibrationally ground state and excited states. This practical QCT method makes it possible to predict reliable quantum-state-resolved S0 of polyatomic molecules on surfaces well below the barrier height and the associated mode-specificity.