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Abstract Energy transferred in atom‐surface collisions typically depends strongly on projectile mass, an effect that can be experimentally detected by isotopic substitution. In this work, we present measurements of inelastic H and D atom scattering from a semiconducting Ge(111)c(2×8) surface exhibiting two scattering channels. The first channel shows the expected isotope effect and is quantitatively reproduced by electronically adiabatic molecular dynamics simulations. The second channel involves electronic excitations of the solid and, surprisingly, exhibits almost no isotope effect. We attribute these observations to scattering dynamics, wherein the likelihood of electronic excitation varies with the impact site engaged in the interaction. Key PointsPrevious work revealed that H atoms with sufficient translational energy can excite electrons over the band gap of a semiconductor in a surface collision.We studied the isotope effect of the energy transfer by H/D substitution and performed band structure calculations to elucidate the underlying excitation mechanism.Our results suggest a site‐specific mechanism that requires the atom to hit a specific surface site to excite an electron‐hole pair. 

Abstract Spillover of adsorbed species from one active site to another is a key step in heterogeneous catalysis. However, the factors controlling this step, particularly the spillover of polyatomic species, have rarely been studied. Herein, we investigate the spillover dynamics of H* and CH₃* species on a single‐atom alloy surface (Rh/Cu(111)) upon the dissociative chemisorption of methane (CH₄), using molecular dynamics that considers both surface phonons and electron‐hole pairs. These dynamical calculations are made possible by a high‐dimensional potential energy surface machine learned from density functional theory data. Our results provide compelling evidence that the H* and CH₃* can spill over on the metal surface at experimental temperatures and reveal novel dynamical features involving an internal motion during diffusion for CH₃*. Increasing surface temperature has a minor effect on promoting spillover, as geminate recombinative desorption becomes more prevalent. However, the poisoning of the active site can be mitigated by the frequent gaseous molecular collisions that occur under ambient pressure in real‐world catalysis, which transfer energy to the trapped adsorbates. Interestingly, the bulky CH₃* exhibits a significant spillover advantage over the light H* due to its larger size, which facilitates energy acquisition. These insights help to advance our understanding of spillover in heterogeneous catalysis. 

Dynamics of molecular interactions with solid surfaces, such as scattering, adsorption/desorption, diffusion, and reaction, are affected by energy dissipation at surfaces. Recent progress in experimental studies of surface dynamics has stimulated intense interest in theoretical investigation of microscopic mechanisms and pathways of energy transfer. This review summarizes recent developments in modeling such processes, emphasizing new understandings of electronically adiabatic and nonadiabatic energy dissipation mechanisms and dynamics in representative systems, using various theoretical methods. In particular, machine learning has been leveraged to represent high-dimensional adiabatic potential energy surfaces, electronic friction tensors, and effective multielectron diabatic Hamiltonians. When integrated with mixed quantum-classical dynamics methods, such as molecular dynamics with electronic friction and independent electron surface hopping, these first-principles-based simulations provided unprecedented insights into the roles played by adiabatic and nonadiabatic energy dissipation channels in surface dynamics and in-depth interpretation of experimental observations. 

The ring polymer molecular dynamics (RPMD) rate theory is an efficient and accurate method for estimating rate coefficients of chemical reactions affected by nuclear quantum effects. The commonly used RPMD treatment of gas-phase bimolecular reactions adopts two dividing surfaces, one at the transition state and another in the reactant asymptote, where the translational partition function is separable from other partition functions and can be readily obtained. With some exceptions, however, this strategy is difficult to implement for processes on surfaces or in solutions, because reactants are often strongly coupled with the extended medium (surface or solvent) and, thus, non-separable. Under such circumstances, the RPMD rate theory with a single dividing surface (SDS) is better suited. However, most of its implementations adopted Cartesian forms of the reaction coordinate, which may not be ideal for describing complex reactions. Here, we present an SDS-based RPMD implementation, which is able to tackle the aforementioned challenges. This approach is demonstrated in four representative reactions, including the gas-phase H + H2 exchange reaction, gas-phase CH3NC isomerization, H recombinative desorption from Pt(111), and NO desorption from Pd(111). This implementation, which is applicable to both uni- and bi-molecular reactions, offers a unified treatment of gas-phase and surface reaction rate calculations on the same footing. 

Although the dynamics of collisions between a molecule and a solid surface are ultimately quantum mechanical, decohering effects owing to the large number of interacting degrees of freedom typically obscure the wavelike nature of these events. However, a partial decoupling of internal molecular motion from external degrees of freedom can reveal striking interference effects despite significant momentum exchange between the molecule and the bath of surface vibrations. We report state-prepared and state-resolved measurements of methane scattering from a room-temperature gold surface that demonstrate total destructive interference between molecular states related by a reflection symmetry operation. High-contrast interference effects prevail for all processes investigated, including vibrationally excited and vibrationally inelastic collisions. The results demonstrate the distinctly quantum mechanical effect of discrete symmetries in molecular collision dynamics.