Resonance Enhancement of Vibrational Polariton Chemistry Obtained from the Mixed Quantum-Classical Dynamics Simulations.

We applied a variety of mixed quantum-classical (MQC) approaches to simulate the VSC-influenced reaction rate constant. All of these MQC simulations treat the key vibrational levels associated with the reaction coordinate in the quantum subsystem (as quantum states), whereas all other degrees of freedom (DOFs) are treated inside the classical subsystem. We find that, as long as we have the quantum state descriptions for the vibrational DOFs, one can correctly describe the VSC resonance condition when the cavity frequency matches the bond vibrational frequency. This correct resonance behavior can be obtained regardless of the detailed MQC methods that one uses. The results suggest that the MQC approaches can generate semiquantitative agreement with the exact results for rate constant changes when changing the cavity frequency, the light-matter coupling strength, or the cavity lifetime. The finding of this work suggests that one can use computationally economic MQC approaches to explore the collective coupling scenario when many molecules are collectively coupled to many cavity modes in the future.

Resonance theory and quantum dynamics simulations of vibrational polariton chemistry.

We present numerically exact quantum dynamics simulations using the hierarchical equation of motion approach to investigate the resonance enhancement of chemical reactions due to the vibrational strong coupling (VSC) in polariton chemistry. The results reveal that the cavity mode acts like a "rate-promoting vibrational mode" that enhances the ground state chemical reaction rate constant when the cavity mode frequency matches the vibrational transition frequency. The exact simulation predicts that the VSC-modified rate constant will change quadratically as the light-matter coupling strength increases. When changing the cavity lifetime from the lossy limit to the lossless limit, the numerically exact results predict that there will be a turnover of the rate constant. Based on the numerical observations, we present an analytic rate theory to explain the observed sharp resonance peak of the rate profile when tuning the cavity frequency to match the quantum transition frequency of the vibrational ground state to excited states. This rate theory further explains the origin of the broadening of the rate profile. The analytic rate theory agrees with the numerical results under the golden rule limit and the short cavity lifetime limit. To the best of our knowledge, this is the first analytic theory that is able to explain the sharp resonance behavior of the VSC-modified rate profile when coupling an adiabatic ground state chemical reaction to the cavity. We envision that both the numerical analysis and the analytic theory will offer invaluable theoretical insights into the fundamental mechanism of the VSC-induced rate constant modifications in polariton chemistry.

Non-adiabatic mapping dynamics in the phase space of the SU(N) Lie group.

We present the rigorous theoretical framework of the generalized spin mapping representation for non-adiabatic dynamics. Our work is based upon a new mapping formalism recently introduced by Runeson and Richardson [J. Chem. Phys. 152, 084110 (2020)], which uses the generators of the su(N) Lie algebra to represent N discrete electronic states, thus preserving the size of the original Hilbert space. Following this interesting idea, the Stratonovich-Weyl transform is used to map an operator in the Hilbert space to a continuous function on the SU(N) Lie group, i.e., a smooth manifold which is a phase space of continuous variables. We further use the Wigner representation to describe the nuclear degrees of freedom and derive an exact expression of the time-correlation function as well as the exact quantum Liouvillian for the non-adiabatic system. Making the linearization approximation, this exact Liouvillian is reduced to the Liouvillian of several recently proposed methods, and the performance of this linearized method is tested using non-adiabatic models. We envision that the theoretical work presented here provides a rigorous and unified framework to formally derive non-adiabatic quantum dynamics approaches with continuous variables and connects the previous methods in a clear and concise manner.

Dehydrogenation of Ammonia Borane by Platinum-Nickel Dimers: Regulation of Heteroatom Interspace Boosts Bifunctional Synergetic Catalysis.

Regulation of the atom-atom interspaces of dual-atom catalysts is essential to optimize the dual-atom synergy to achieve high activity but remains challenging. Herein, we report an effective strategy to regulate the Pt1 -Ni1 interspace to achieve Pt1 Ni1 dimers and Pt1 +Ni1 heteronuclear dual-single-atom catalysts (HDSACs) by tailoring steric hindrance between metal precursors during synthesis. Spectroscopic characterization reveals obvious electron transfers in Pt1 Ni1 oxo dimers but not in Pt1 +Ni1 HDSAC. In the hydrolysis of ammonia borane (AB), the H2 formation rates show an inverse proportion to the Pt1 -Ni1 interspace. The rate of Pt1 Ni1 dimers is ≈13 and 2 times higher than those of Pt1 and Pt1 +Ni1 HDSAC, manifesting the interspace-dependent synergy. Theoretical calculations reveal that the bridging OH group in Pt1 Ni1 dimers promotes water dissociation, while Pt1 facilitates the cleavage of B-H bonds in AB, which boosts a bifunctional synergy to accelerate H2 production cooperatively.

Synthesis of Quasi-Bilayer Subnano Metal-Oxide Interfacial Cluster Catalysts for Advanced Catalysis.

Planar metal clusters possess high metal utilization, distinct electronic properties, and catalytic functions from their 3D counterparts. However, synthesis of these materials is challenging due to much elevated surface free energies. Here it is reported that silica supported planar bilayer Pt-CoOx subnano clusters, consisting of approximately one atomic layer of Pt and one CoOx layer on top, can be achieved by employing strong-electrostatic interactions during impregnation and precisely-controlled CoOx coating using atomic layer deposition. Such bilayer structure is unambiguously confirmed by electron microscopy and in situ X-ray absorption fine spectroscopy which is never reported before. This synthetic approach can be extended to another eight permutations of planar metal-oxide subnano clusters. The resulting bilayer catalysts, owing to unique electronic properties and the abundant metal-oxide interfaces created, exhibit excellent catalytic performances in the reactions of preferential oxidation of CO in H2 and selective hydrogenation of acetylene, by showing much higher selectivity and intrinsic activities at least 8 and 48 times greater than those conventional oxide coated 3D metal clusters/nanoparticles, highlighting the advances of bilayer interfacial structure. These findings open a new avenue to design abundant and highly active metal-oxide interfaces for advanced metal catalysis.