Article
Physics, Fluids & Plasmas
Philipp Stroeker, Karsten Meier
Summary: The methodology developed by Lustig is applied to derive rigorous expressions for thermodynamic properties of fluids in the grand canonical ensemble, which are expressed by phase-space functions related to derivatives of the grand canonical potential. The derived expressions are validated by Monte Carlo simulations, providing more reliable results compared to previous literature and becoming equivalent to corresponding expressions in the canonical ensemble in the thermodynamic limit.
Article
Mechanics
Dam Thanh Son, Mikhail Stephanov, Ho-Ung Yee
Summary: The study discusses the dependence of the phase diagram of a hypothetical isotope of helium with nuclear mass less than 4 atomic mass units. As the nuclear mass decreases, the temperatures of the superfluid phase transition and the liquid-gas critical point show different trends. Various scenarios are proposed, ruling out the simplest scenario through analysis of the Landau theory and suggesting a more likely sequence of changes in the phase diagram with decreasing nuclear mass.
JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT
(2021)
Article
Optics
Renato Pessoa, S. A. Vitiello, L. A. Pena Ardila
Summary: The properties of polarons in an ultracold Fermi gas were studied using Quantum Monte Carlo techniques and both zero-range and square-well potential models. The polaron effective mass, binding energy, and effective coupling were computed, with the latter obtained using Landau-Pomeranchuk's weakly interacting quasiparticle model. The contact parameter was estimated by fitting the pair distribution function of atoms in different spin states.
Article
Materials Science, Multidisciplinary
Massimo Boninsegni
Summary: The bound state of a He-3 atom at the interface between crystalline and superfluid phases of He-4 is investigated using first principle Quantum Monte Carlo simulations. The results show that the He-3 atom is sharply localized in a quasi-2D layer of He-4, located in the intermediate region between the solid and liquid states. The localization and quantum-mechanical exchanges of the He-3 atom are influenced by the attractive strength of the substrate.
RESULTS IN PHYSICS
(2022)
Article
Physics, Multidisciplinary
J. Salort, F. Chilla, E. Rusaouen, P-E Roche, M. Gibert, I Moukharski, A. Braslau, F. Daviaud, B. Gallet, E-W Saw, B. Dubrulle, P. Diribarne, B. Rousset, M. Bon Mardion, J-P Moro, A. Girard, C. Baudet, V L'vov, A. Golov, S. Nazarenko
Summary: Measurements of velocity in turbulent superfluid helium between co-rotating propellers reveal differences between quantum and classical turbulence, with an excess of energy at small scales in the quantum case. This difference is attributed to a pileup of superfluid kinetic energy at the bottom of the inertial cascade of turbulence due to a specific dissipation mechanism.
NEW JOURNAL OF PHYSICS
(2021)
Article
Chemistry, Physical
Tina N. Mihm, William Z. Van Benschoten, James J. Shepherd
Summary: A new approach using low-cost calculations was developed to find a twist angle that matches the coupled cluster doubles energy in a finite unit cell. The method was shown to have comparable accuracy with exact methods beyond coupled cluster doubles theory. Additionally, for small system sizes, the same twist angle can be found by comparing energies directly, suggesting a potential route towards twist angle selection.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Massimo Boninsegni, Saverio Moroni
Summary: The second layer of 4He adsorbed on a graphite substrate is studied using Quantum Monte Carlo simulations. The substrate's corrugation is fully taken into account in a microscopic model, and the results are compared to those obtained with a smooth substrate. The main effect of the corrugation is a 20% reduction in the superfluid fraction of the top layer at zero temperature. No evidence of any commensurate (7/12) crystalline and/or supersolid phase is found, and the superfluid transition temperature is estimated to be -0.75 K. The implications of these findings on recent experiments are discussed.
RESULTS IN PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Leon Otis, Eric Neuscamman
Summary: We discuss recent progress in excited-state-specific quantum chemistry and quantum Monte Carlo and show how combining methods from these fields can predict excited states accurately. Important advances in both fields include improved optimization methods, handling of complicated wave function forms, and balancing the quality of wave functions for ground and excited states. Demonstrations using a combination of specific quantum chemistry and variational Monte Carlo show that this approach is more reliable and accurate than other high-level methods and can provide clarity in cases where existing methods do not agree.
WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE
(2023)
Article
Physics, Applied
Massimo Boninsegni
Summary: First-principle computer simulations show no evidence of a liquid top layer or proximity to a superfluid transition in a thin parahydrogen film adsorbed on a silica substrate at low temperatures, contradicting recent experimental claims. The top layer is found to be an insulating crystal without quantum-mechanical exchanges between molecules, consistent with observations on other substrates.
JOURNAL OF LOW TEMPERATURE PHYSICS
(2021)
Article
Chemistry, Physical
B. P. Akhouri, J. R. Solana
Summary: The equilibrium thermodynamic properties of binary Lennard-Jones mixtures are studied using a Monte Carlo-based perturbation theory. The results are compared with simulation data for two equimolar binary Lennard-Jones fluid mixtures at different temperatures and densities. The approach seems to be accurate and useful for studying mixtures with various intermolecular interactions, including real fluid mixtures.
MOLECULAR SIMULATION
(2023)
Article
Physics, Multidisciplinary
Sergio Contreras, Alejandro Gil-Villegas
Summary: Computer simulations and theoretical results of N Quantum Hard Spheres (QHS) particles show that analytical results can be provided for extreme and maximum confinement based on an extension of the Helmholtz free energies for classical systems.
Article
Physics, Multidisciplinary
Matteo Ciardi, Tommaso Macri, Fabio Cinti
Summary: This work explores methodology for investigating interacting systems with contact interactions, introducing a class of zonal estimators for path-integral Monte Carlo methods aimed at providing physical information about limited regions of inhomogeneous systems. The usefulness of zonal estimators is demonstrated through their application to a system of trapped bosons in a quasiperiodic potential in two dimensions, focusing on finite temperature properties across a wide range of potential values. Finally, the generalization of such estimators to local fluctuations of particle numbers and magnetic ordering in multi-component systems, spin systems, and systems with nonlocal interactions is discussed.
Article
Chemistry, Physical
Oliver A. Bramley, Timothy J. H. Hele, Dmitrii Shalashilin
Summary: Zombie states are a formalism that describes coupled coherent fermionic states in a computationally tractable manner. This study extends the previous work on Zombie states and develops efficient algorithms for evaluating operators and addressing normalization. It also presents techniques for improving accuracy and calculating low-lying excited states.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Jacob I. Monroe, William P. Krekelberg, Austin McDannald, Vincent K. Shen
Summary: We introduce Gaussian Process Regression (GPR) as an enhanced method of thermodynamic extrapolation and interpolation. The heteroscedastic GPR models automatically weight provided information by its estimated uncertainty, allowing for the incorporation of highly uncertain derivative information. We apply GPR models to various data sources and assess active learning strategies, and finally apply it to tracing vapor-liquid equilibrium for a single-component Lennard-Jones fluid.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Luca Maffioli, Edward R. Smith, James P. Ewen, Peter J. Daivis, Daniele Dini, B. D. Todd
Summary: This study derives the transient-time correlation function (TTCF) expression for the computation of phase variables in inhomogenous confined atomistic fluids undergoing boundary-driven planar shear flow. The TTCF method is then applied to compute the shear stress and slip velocity for atomistic fluids at low shear rates under constant pressure and constant volume conditions. The results show that the TTCF method significantly improves the accuracy compared to direct averaging of multiple trajectories, making it suitable for studying the tribology and rheology of confined fluids at realistic flow rates.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Physics, Atomic, Molecular & Chemical
L. I. Kolesnikova, L. Yu. Rusin, M. B. Sevryuk
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2015)
Article
Mathematics, Applied
Mikhail B. Sevryuk
REGULAR & CHAOTIC DYNAMICS
(2016)
Article
Mathematics, Applied
Mikhail B. Sevryuk
REGULAR & CHAOTIC DYNAMICS
(2017)
Article
Mathematics, Applied
Vincenzo Aquilanti, Andrea Lombardi, Mikhail B. Sevryuk
REGULAR & CHAOTIC DYNAMICS
(2014)
Article
Mathematics, Applied
Mikhail B. Sevryuk
REGULAR & CHAOTIC DYNAMICS
(2014)
Article
Physics, Atomic, Molecular & Chemical
L. I. Kolesnikova, L. Yu Rusin, M. B. Sevryuk
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2013)
Article
Physics, Atomic, Molecular & Chemical
E. V. Ermolova, L. Yu Rusin, M. B. Sevryuk
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2014)
Article
Mathematics
Mikhail B. Sevryuk
Summary: This paper presents examples of Hamiltonian and reversible systems with smooth d-parameter families of invariant n-tori carrying conditionally periodic motions. The cases of isotropic, coisotropic, and atropic tori in non-compact and compact phase spaces are considered. Additionally, an example of an analytic Hamiltonian system with an isolated invariant N-torus carrying conditionally periodic motions is presented for any N >= 3.
INDAGATIONES MATHEMATICAE-NEW SERIES
(2021)
Article
Chemistry, Physical
Vyacheslav M. Akimov, Vladimir M. Azriel', Ekaterina V. Ermolova, Dmitrii B. Kabanov, Lyubov' I. Kolesnikova, Lev Yu. Rusin, Mikhail B. Sevryuk
Summary: This paper investigates the detailed dynamics of direct three-body ion-ion recombination reactions, considering the main aspects of non-central ion encounters. The reactions are simulated using the quasiclassical trajectory method with diabatic semiempirical potential energy surfaces. The recombination mechanisms are studied through visualization of randomly selected trajectories, and a comparison is made between trajectories with identical initial conditions for different systems.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Multidisciplinary Sciences
Vyacheslav M. Akimov, Vladimir M. Azriel, Ekaterina V. Ermolova, Dmitrii B. Kabanov, Lev Yu. Rusin, Mikhail B. Sevryuk
Summary: By simulating the dynamics of bimolecular recombination reactions under different conditions, it was found that the collision energy has important effects on the recombination cross section and the energy distribution of products. The type of halide ion also plays a significant role in the dynamics.
RENDICONTI LINCEI-SCIENZE FISICHE E NATURALI
(2022)
Article
Chemistry, Physical
Vyacheslav M. Akimov, Vladimir M. Azriel, Ekaterina Ermolova, Dmitrii B. Kabanov, Lyubov' Kolesnikova, Lev Yu Rusin, Mikhail B. Sevryuk
Summary: The direct three-body recombination reactions Cs+ + X- + R -> CsX + R (X = F, I and R = Ar, Xe) were studied using the quasiclassical trajectory method, revealing the distinct features of different recombination pairs and the superior efficiency of xenon in accepting excess energy from ion pairs. The resulting energy distributions of the recombination products show equilibrium for rotational energy in CsF and CsI molecules, but strong non-equilibrium for vibrational energy.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
Article
Multidisciplinary Sciences
Vyacheslav M. Akimov, Vladimir M. Azriel, Lyubov I. Kolesnikova, Lev Yu. Rusin, Mikhail B. Sevryuk
RENDICONTI LINCEI-SCIENZE FISICHE E NATURALI
(2019)
Article
Physics, Atomic, Molecular & Chemical
V. M. Azriel', V. M. Akimov, E. V. Ermolova, D. B. Kabanov, L. I. Kolesnikova, L. Yu. Rusin, M. B. Sevryuk
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2018)
Article
Physics, Atomic, Molecular & Chemical
V. M. Azriel', V. M. Akimov, E. V. Ermolova, L. I. Kolesnikova, L. Yu. Rusin, M. B. Sevryuk
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2018)
Article
Mathematics, Applied
Mikhail B. Sevryuk
MOSCOW MATHEMATICAL JOURNAL
(2017)