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A full-dimensional global potential energy surface (PES) for the H2 + N2 system is constructed using the permutation invariant polynomial-neural network method, based on high-level ab initio energy points computed at the CCSD(T)-F12a/AVQZ level. To accurately describe the long-range interactions, a multipole expansion parameterized by ab initio data is incorporated into the PES. Quantum close-coupling scattering calculations are reported for rotationally inelastic transitions in H2 + N2 collisions using the full-dimensional PES. Cross sections for rotational excitation of N2 within a rigid rotor model are found to be in excellent agreement with those obtained using a four-dimensional (4D) PES reported by Gomez et al. [Chem. Phys. Lett. 445, 99 (2007)]. Cross sections for pure rotational quenching of H2, as well as quenching of H2 accompanied by rotational excitation of N2, exhibit dense resonance structures. For collision energies above 2.0 cm−1, the results are in close agreement with those obtained using the 4D PES of Gomez et al., including the positions of the sharp resonances. At lower collision energies, however, noticeable differences appear, indicating a strong sensitivity of the resonance features to the PES in this regime. An accurate simulation of energy transfer in collisions between rovibrationally excited H2 and D2 with N2 can now be addressed using the full-dimensional PES reported in this study. 

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. 

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.