A modified generalized Langevin oscillator model for activated gas-surface reactions

Surface motion has proven to influence the gas-surface reactions in various ways. An adequate model to describe the complex lattice effects in a relatively simple way is therefore highly desirable. In this work, we have modified the widely used Generalized Langevin Oscillator (GLO) model to incorporate the molecule-surface coupling that plays an important role in activated dissociation of polyatomic molecules on metal surfaces. To this end, taking the well-studied CHD₃+Ni(111) system as an example, we add a coupling potential linearly dependent on the surface oscillating coordinate, which becomes essential in predicting the dissociative sticking coefficients for reactive scattering. We further scale the mass of the surface oscillator on the basis of a mechanic coupling parameter, which has significantly improved the description of the molecule-surface energy transfer for nonreactive scattering. This so-called modified GLO (MGLO) model retains the simplicity and advantages of the original GLO, while yields much more accurate dynamics results that are in remarkably good agreement with the benchmark data calculated using ab initio molecular dynamics. We argue that the MGLO model is applicable to these highly activated gas-surface reactions with strong molecule-surface couplings.