Jeremy Richardson

Last Name

Richardson

First Name

Jeremy

ORCID

0000-0002-9429-151X

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09602 - Richardson, Jeremy / Richardson, Jeremy

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Publications 1 - 10 of 56

Quantum Tunnelling Driven H2 Formation on Graphene
Han, Erxun; Fang, Wei; Stamatakis, Michail; et al. (2022)
The Journal of Physical Chemistry Letters
It is commonly believed that it is unfavorable for adsorbed H atoms on carbonaceous surfaces to form H2 without the help of incident H atoms. Using ring-polymer instanton theory to describe multidimensional tunnelling eﬀects, combined with ab initio electronic structure calculations, we ﬁnd that these quantum-mechanical simulations reveal a qualitatively diﬀerent picture. Recombination of adsorbed H atoms, which was believed to be irrelevant at low temperature due to high barriers, is enabled by deep tunnelling, with reaction rates enhanced by tens of orders of magnitude. Furthermore, we identify a new path for H recombination that proceeds via multidimensional tunnelling but would have been predicted to be unfeasible by a simple one-dimensional description of the reaction. The results suggest that hydrogen molecule formation at low temperatures are rather fast processes that should not be ignored in experimental settings and natural environments with graphene, graphite, and other planar carbon segments.
Quantum entanglement from classical trajectories
Runeson, Johan E.; Richardson, Jeremy (2021)
arXiv
A long-standing challenge in mixed quantum-classical trajectory simulations is the treatment of entanglement between the classical and quantal degrees of freedom. We present a novel approach which describes the emergence of entangled states entirely in terms of independent and deterministic Ehrenfest-like classical trajectories. For a two-level quantum system in a classical environment, this is derived by mapping the quantum system onto a path-integral representation of a spin-1/2. We demonstrate that the method correctly accounts for coherence and decoherence and thus reproduces the splitting of a wavepacket in a nonadiabatic scattering problem. This discovery opens up a new class of simulations as an alternative to stochastic surface-hopping, coupled-trajectory or semiclassical approaches.
Transfer Learning for Affordable and High-Quality Tunneling Splittings from Instanton Calculations
Käser, Silvan; Richardson, Jeremy; Meuwly, Markus (2022)
Journal of Chemical Theory and Computation
The combination of transfer learning (TL) a low-level potential energy surface (PES) to a higher level of electronic structure theory together with ring-polymer instanton (RPI) theory is explored and applied to malonaldehyde. The RPI approach provides a semiclassical approximation of the tunneling splitting and depends sensitively on the accuracy of the PES. With second-order Møller–Plesset perturbation theory (MP2) as the low-level model and energies and forces from coupled cluster singles, doubles, and perturbative triples [CCSD(T)] as the high-level (HL) model, it is demonstrated that CCSD(T) information from only 25–50 judiciously selected structures along and around the instanton path suffice to reach HL accuracy for the tunneling splitting. In addition, the global quality of the HL-PES is demonstrated through a mean average error of 0.3 kcal/mol for energies up to 40 kcal/mol above the minimum energy structure (a factor of 2 higher than the energies employed during TL) and <2 cm–1 for harmonic frequencies compared with computationally challenging normal mode calculations at the CCSD(T) level.
Attosecond spectroscopy of molecular charge transfer uncovers a 1.5-fs delay in population transfer
Matselyukh, Danylo T.; Rott, Florian; Schnappinger, Thomas; et al. (2025)
Nature Communications
The transfer of population between two intersecting quantum states is the most fundamental event in many dynamical processes in physics, chemistry, biology, and material science. Any two-state description of such processes requires population leaving one state to instantaneously appear in the other. We show that coupling to additional states, present in all real-world systems, can cause a measurable delay in population transfer. Using attosecond spectroscopy supported by quantum-chemical calculations, we measure a delay of 1.46 ± 0.41 fs at a charge-transfer crossing in CF3I+, where an electron hole moves from the fluorine atoms to iodine. Our measurements also resolve the other fundamental quantum-dynamical processes involved in the charge-transfer reaction: a vibrational rearrangement time of 9.38 ± 0.21 fs (during which the vibrational wave packet travels to the state crossing) and a population-transfer time of 2.3–2.4 fs. Our work shows that delays in population transfer readily appear in otherwise-adiabatic reactions and predicts them to be on the order of a single-femtosecond for molecular valence-state crossings. These results have implications for many research areas, such as atomic and molecular physics, charge transfer, or light harvesting.
Mechanistic Insights into Nitroarene Hydrogenation Dynamics on Pt(111) via In Situ Tip-Enhanced Raman Spectroscopy
Cai , Zhen-Feng; Manae, Meghna A.; Tang , Zi-Xi; et al. (2025)
Journal of the American Chemical Society
Mechanistic insights into the molecular-level dynamics of nitroarene hydrogenation on Pt remain limited, largely because most prior studies rely on ex situ, ensemble-averaged measurements, or simulations considered in isolation. Here, we address this gap and demonstrate a novel methodology combining in situ tip-enhanced Raman spectroscopy (TERS) with density functional theory (DFT) modeling to track, at a well-defined single plasmonic junction, the hydrogenation of chloronitrothiophenol (CNTP) on atomically flat Pt(111). In situ TERS captures the dynamic transformation of CNTP → chloroaminothiophenol (CATP) under ambient H2exposure with a characteristic time scale of ∼6 s. Complementary DFT modeling maps the reaction energetics, revealing novel mechanistic insights: CNTP desorption is rapid initially (barrier 0.61 eV) but slows down once the Pt(111) surface is at about half-coverage; molecular bending on the half-covered Pt(111) surface is barrierless and exergonic; the first hydrogen addition to CNTP is facile (barrier 0.26 eV), while the second hydrogen addition is kinetically most demanding (barrier 0.83 eV), yielding a time scale of seconds that matches experimental results and identifies the rate-determining step. These findings advance molecular-level understanding of nitroarene hydrogenation on Pt(111) and demonstrate in situ TERS integrated with first-principles DFT modeling as a powerful platform for operando mechanistic studies of heterogeneous catalytic processes at the nanoscale.
Nonadiabatic Dynamics with the Mapping Approach to Surface Hopping (MASH)
Richardson, Jeremy; Lawrence, Joseph; Mannouch, Jonathan R. (2025)
Annual Review of Physical Chemistry
The mapping approach to surface hopping (MASH) combines the rigor of quasiclassical mapping approaches with the pragmatism of surface hopping to obtain a practical trajectory-based method for simulating nonadiabatic dynamics in molecular systems. In this review, we outline the derivation of MASH, prove a number of important properties that ensure its reliability, and illustrate its accuracy for computing nonadiabatic rate constants as well as ultrafast photochemical dynamics.
Using Instanton Theory to Study Quantum Effects in Photosensitization
Manae, Meghna A.; Richardson, Jeremy (2024)
Chimia
Electronic excitation is usually accomplished using light (photoexcitation) and is a key step in a vast number of important physical and biological processes. However, in instances where photoexcitation is not possible, a photosensitizer can excite the target molecule in a process called photosensitization. Unfortunately, full details of its mechanism are still unknown. This perspective gives an overview of the current understanding of photosensitization and describes how instanton theory can be used to fill the gaps, especially with regard tothe importance of quantum tunnelling effects.
The exact tunnelling splitting of malonaldehyde from symmetrized path-integral molecular dynamics
Baumann, Jonah; Trenins, George; Richardson, Jeremy (2025)
Molecular Physics
A recently proposed path-integral molecular dynamics method is applied to compute the tunnelling splitting of malonaldehyde. The approach, which is based on symmetrised partition functions, rigorously projects out the ground rotational state and is formally exact for a given potential energy surface (PES). We obtain the result of 21.1±0.1cm−1, which can be compared with previous calculations on the same PES, including diffusion Monte Carlo (21.0±0.4cm−1) and a grid-based wavefunction method (21.7±0.3cm−1), as well as with experiment (21.6cm−1). This resolves the discrepancies of previous PIMD studies (19.3±0.2cm−1), which we find to be contaminated by contributions from higher rotational states. Our work demonstrates the accuracy that can be achieved from path-integral methods in polyatomic molecules and sets the stage for exact tunnelling-splitting calculations in even larger systems out of the range of traditional methods.
Nonadiabatic instanton rate theory beyond the golden-rule limit
Trenins, George; Richardson, Jeremy (2022)
The Journal of Chemical Physics
Fermi’s golden rule (GR) describes the leading-order behavior of the reaction rate as a function of the diabatic coupling. Its asymptotic (ℏ → 0) limit is the semiclassical golden-rule instanton rate theory, which rigorously approximates nuclear quantum effects, lends itself to efficient numerical computation, and gives physical insight into reaction mechanisms. However, the golden rule by itself becomes insufficient as the strength of the diabatic coupling increases, so higher-order terms must be additionally considered. In this work, we give a first-principles derivation of the next-order term beyond the golden rule, represented as a sum of three components. Two of them lead to new instanton pathways that extend the GR case and, among other factors, account for effects of recrossing on the full rate. The remaining component derives from the equilibrium partition function and accounts for changes in potential energy around the reactant and product wells due to diabatic coupling. The new semiclassical theory demands little computational effort beyond a GR instanton calculation. It makes it possible to rigorously assess the accuracy of the GR approximation and sets the stage for future work on general semiclassical nonadiabatic rate theories.
Quantum tunnelling pathways of the water pentamer
Cvitaš, Marko T.; Richardson, Jeremy (2020)
Physical Chemistry Chemical Physics
We apply the semiclassical instanton method to calculate all feasible tunnelling pathways in the water pentamer. Similarly to the water trimer, there are labile flip dynamics as well as a number of different bifurcation pathways coupled to flips. In contrast to the trimer, puckering motion of the oxygen ring makes the ring-polymer instanton approach difficult to converge, a problem which is resolved by using a recently developed time-independent formalism of the method. We use the results to predict the complete ground-state tunnelling splitting pattern of 320 states, which should help in the continuing effort to assign the experimental spectrum. A comparison between the rearrangement pathways in the water trimer and pentamer sheds light on the many-body cooperative effects of hydrogen bonding which are important for a full understanding of the liquid state.

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Jeremy Richardson

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