Modeling Electronic Structure And Dynamics Of Molecules On Metal Surfaces

Molecular dynamics near metal surfaces underlie a number of fields in chemistry, including chemisorption, electrochemistry, heterogeneous catalysis, and many others. Due to the continuum of electronic states possessed by metals, electron-hole pairs can be easily excited by moving molecules near metals. Consequently, molecular dynamics near metal surfaces often go beyond the Born-Oppenheimer approximation by demanding, e.g., a friction and its accompanied random force, or a surface hopping approach. In this thesis, we first propose an efficient and accurate interpolation method for computing the electronic friction tensor as appropriate for molecular dynamics. Unlike traditional methods based on broadening, our interpolation method relies only on orbital energy gradients (rather than derivative couplings), and does not involve any user-identified parameters. Next, we develop several configuration interaction approaches for characterizing the electronic structure of model molecule-metal system. Based on these approaches, we introduce an efficient reduced representation with a special focus on the molecular charge character. Thereafter, we modify the fewest switches surface hopping (FSSH) method to accommodate this reduced representation by including electronic relaxation (ER). The reduced representation and the FSSH-ER together form a new surface hopping scheme for modeling molecular nonadiabatic dynamics. This scheme is valid across a wide range of coupling strength as supported by tests applied to the Anderson-Holstein model for electron transfer.