A simplification of the Heller-Herman-Kluk-Kay (HK) propagator is presented that does not suffer from the need for an increasing number of trajectories with dimensions of the system under study. This is accomplished by replacing HK's uniformizing integral over all of phase space by a one-dimensional curve that is appropriately selected to lie along the fastest growing manifold of a defining trajectory. It is shown that this modification leads to eigenspectra of quantum states in weakly anharmonic systems that can outperform the comparatively computationally cheap thawed Gaussian approximation method and frequently approach the accuracy of spectra obtained with the full HK propagator.
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http://dx.doi.org/10.1063/1.4901301 | DOI Listing |
Soft Matter
November 2024
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China.
The "classical" thermodynamic and statistical mechanical theories of Gibbs and Boltzmann are both predicated on axiomatic assumptions whose applicability is hard to ascertain. Theoretical objections and an increasing number of observed deviations from these theories have led to sustained efforts to develop an improved mathematical and physical foundation for them, and the search for appropriate extensions that are generally applicable to condensed materials at low temperatures () and high material densities where the assumptions of these theories start to become particularly questionable. These theoretical efforts have largely focused on minimal models of condensed material systems, such as the Fermi-Ulam-Pasta-Tsingou model, and other simplified models of condensed materials that are amenable to numerical and analytic treatments and that can serve to illuminate essential features of relaxation processes in condensed materials under conditions approaching integrable dynamics where clear departures from classical thermodynamics and dynamics can be generally expected.
View Article and Find Full Text PDFPhys Chem Chem Phys
August 2024
School of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China.
Monolayer CdGaInS is an excellent optoelectronic material, but its thermoelectric properties remain unexplored. Through first-principles studies, we investigate the thermoelectric transport properties of monolayer CdGaInS. The results show that the degenerate weakly dispersive valence band results in an ultrahigh Seebeck coefficient, and the small parabolic electron pockets lead to good electron mobility and conductivity.
View Article and Find Full Text PDFJ Comput Chem
September 2024
ENSL, CNRS, Laboratoire de Chimie UMR 5182, Lyon Cedex, France.
Density functional theory (DFT) calculations explore the stability of a single platinum atom on various flat, stepped, and defective ceria surfaces, in the context of single-atom catalysts (SACs) for the water-gas shift (WGS) reaction. The adsorption properties and diffusion kinetics of the metal strongly depend on the support termination with large stability on metastable and stepped CeO(100) and (210) surfaces where the diffusion of the platinum atom is hindered. At the opposite, the more stable CeO(111) and (110) terminations weakly bind the platinum atom and can promote the growth of metallic clusters thanks to fast diffusion kinetics.
View Article and Find Full Text PDFPhys Rev Lett
March 2024
J. Stefan Institute, 1000 Ljubljana, Slovenia.
We investigate full quantum mechanical evolution of two electrons nonlinearly coupled to quantum phonons and simulate the dynamical response of the system subject to a short spatially uniform optical pulse that couples to dipole-active vibrational modes. Nonlinear electron-phonon coupling can either soften or stiffen the phonon frequency in the presence of electron density. In the former case, an external optical pulse tuned just below the phonon frequency generates attraction between electrons and leads to a long-lived bound state even after the optical pulse is switched off.
View Article and Find Full Text PDFJ Chem Phys
March 2024
Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
We investigate the endofullerene system 3He@C60 with a four-dimensional potential energy surface (PES) to include the three He translational degrees of freedom and C60 cage radius. We compare second order Møller-Plesset perturbation theory (MP2), spin component scaled-MP2, scaled opposite spin-MP2, random phase approximation (RPA)@Perdew, Burke, and Ernzerhof (PBE), and corrected Hartree-Fock-RPA to calibrate and gain confidence in the choice of electronic structure method. Due to the high cost of these calculations, the PES is interpolated using Gaussian Process Regression (GPR), owing to its effectiveness with sparse training data.
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