We develop a general quantum theory for reactive collisions involving power-law potentials (-1/r(n)) valid from the ultracold up to the high-temperature limit. Our quantum defect framework extends the conventional capture models to include the nonuniversal case when the short-range reaction probability P(re)<1. We present explicit analytical formulas as well as numerical studies for the van der Waals (n=6) and polarization (n=4) potentials. Our model agrees well with recent merged beam experiments on Penning ionization, spanning collision energies from 10 mK to 30 K [Henson et al., Science 338, 234 (2012)].
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http://dx.doi.org/10.1103/PhysRevLett.110.213202 | DOI Listing |
J Chem Theory Comput
January 2025
Department of Chemistry, Rice University, Houston, Texas 77005-1892, United States.
Generalized Hartree-Fock (GHF) is a long-established electronic structure method that can lower the energy (compared to spin-restricted variants) by breaking physical wave function symmetries, namely and . After an exposition of GHF theory, we assess the use of GHF trial wave functions in phaseless auxiliary field quantum Monte Carlo (ph-AFQMC-G) calculations of strongly correlated molecular systems including symmetrically stretched hydrogen rings, carbon dioxide, and dioxygen. Imaginary time propagation is able to restore symmetry and yields energies of comparable or better accuracy than CCSD(T) with unrestricted HF and GHF references, and consistently smooth dissociation curves─a remarkable result given the relative scalability of ph-AFQMC-G to larger system sizes.
View Article and Find Full Text PDFBiomed Opt Express
January 2025
Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Optical coherence tomography angiography (OCTA) offers unparalleled capabilities for non-invasive detection of vessels. However, the lack of accurate models for light-tissue interaction in OCTA jeopardizes the development of the techniques to further extract quantitative information from the measurements. In this manuscript, we propose a Monte Carlo (MC)-based simulation method to precisely describe the signal formation of OCTA based on the fundamental theory of light-tissue interactions.
View Article and Find Full Text PDFJ Chem Theory Comput
January 2025
Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas 76019, United States.
Integrating machine learning potentials (MLPs) with quantum mechanical/molecular mechanical (QM/MM) free energy simulations has emerged as a powerful approach for studying enzymatic catalysis. However, its practical application has been hindered by the time-consuming process of generating the necessary training, validation, and test data for MLP models through QM/MM simulations. Furthermore, the entire process needs to be repeated for each specific enzyme system and reaction.
View Article and Find Full Text PDFJ Chem Theory Comput
January 2025
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
We present an implementation of the quantum mechanics/molecular mechanics (QM/MM) method for periodic systems using GPU accelerated QM methods, a distributed multipole formulation of the electrostatics, and a pseudobond treatment of the QM/MM boundary. We demonstrate that our method has well-controlled errors, stable self-consistent QM convergence, and energy-conserving dynamics. We further describe an application to the catalytic kinetics of chorismate mutase.
View Article and Find Full Text PDFJ Chem Phys
January 2025
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan.
The quantum-electrodynamic non-adiabatic emission (QED-NAE) is a type of radiatively assisted vibronic de-excitation due to electromagnetic vacuum fluctuations on non-adiabatic processes. Building on our previous work [Tsai et al., J.
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