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
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
Optics
Stefano Baroni
Summary: This study presents a different approach to Rayleigh-Schrodinger perturbation theory, using Laplace transforms and polynomial theory, to calculate the perturbative expansion of the energy of a quantum system's nondegenerate ground state. The method is easily applicable to symbolic computation. A stochastic interpretation of the perturbative corrections leads to a resummation scheme equivalent to the reptation quantum Monte Carlo method.
Article
Chemistry, Physical
Jonas Feldt, Antoine Bienvenu, Roland Assaraf
Summary: In this paper, a new estimator in the variational Monte Carlo framework is proposed, which utilizes numerically cheap single-core subsamplings to improve the estimation of molecular properties. Furthermore, a spin-dependent core definition is introduced to simplify the algorithm and enhance its efficiency.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Giovani L. Rech, Andre L. Martinotto, Janete E. Zorzi, Claudio A. Perottoni
Summary: The relative stability between the crystal structure of alpha-F-2, space group C2/c, and a hypothesized high-pressure phase, space group Cmce, was investigated using Density Functional Theory and Quantum Monte Carlo calculations. The analysis of the phonon dispersion spectra showed that the Cmce phase exhibits dynamical instability near the Gamma-point at ambient pressure, which disappears under increasing pressure. This instability is attributed to the absence of sigma-holes in the fluorine molecule, resulting in repulsive head-to-head interactions between molecules.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Yuichi Motoyama, Kazuyoshi Yoshimi, Junya Otsuki
Summary: Analytic continuation from the imaginary-time Green's function to the spectral function is crucial for studying the dynamical properties of quantum many-body systems. However, this process is unstable and has advantages and disadvantages. Combining SpM AC with Pade approximation in the SpM-Pade method can provide more accurate and stable results.
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
Multidisciplinary Sciences
Yan-Cheng Wang, Meng Cheng, William Witczak-Krempa, Zi Yang Meng
Summary: The experimental discovery of Anyons in two-dimensional electron gases has opened up new possibilities for studying quantum particles beyond bosons and fermions. Large-scale quantum Monte Carlo simulations have revealed unique conductivity properties near a phase transition, with implications for quantum materials research.
NATURE COMMUNICATIONS
(2021)
Article
Multidisciplinary Sciences
Jan Kessler, Francesco Calcavecchia, Thomas D. Kuehne
Summary: Inspired by the universal approximation theorem and the widespread adoption of artificial neural network techniques, feed-forward neural networks are proposed as a general purpose trial wave function for quantum Monte Carlo simulations of continuous many-body systems. The accuracy of the trial wave functions was demonstrated by studying an exactly solvable model system of two trapped interacting particles and the hydrogen dimer. The whole many-body wave function can be represented by a neural network for simple model systems, while the antisymmetry condition of non-trivial fermionic systems is incorporated by means of a Slater determinant.
ADVANCED THEORY AND SIMULATIONS
(2021)
Article
Physics, Multidisciplinary
Julia A. Davies, Christoph Schran, Fabien Brieuc, Dominik Marx, Andrew M. Ellis
Summary: In this study, infrared spectroscopy is used to investigate 4HeN center dot center dot center dot H3O+ complexes. It is found that the rotational behavior of H3O+ undergoes significant changes as 4He atoms are added.
PHYSICAL REVIEW LETTERS
(2023)
Article
Chemistry, Physical
Francisco Ballesteros, Shelbie Dunivan, Ka Un Lao
Summary: This work reports benchmark binding energies for dispersion-bound complexes, DNA-ellipticine intercalation complex, and buckycatcher-C-60 complex with 120 heavy atoms using a focal-point method based on MP2 and CCSD(T) extrapolated to the CBS limit. The discrepancies between CCSD(T) and fixed-node diffusion Monte Carlo methods are substantial for large noncovalent complexes.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Jun-Han Huang, Guang-Ming Zhang, Dao-Xin Yao
Summary: By using quantum Monte Carlo simulations and stochastic analytic continuation, this study investigates the dynamical spin excitations of a one-dimensional S = 1 Heisenberg antiferromagnetic chain with single-ion anisotropy. A quantum phase transition and fractionalized spinons as elementary excitations were observed at the critical point, showing similarities with a S = 1/2 Heisenberg antiferromagnetic chain.
Article
Materials Science, Multidisciplinary
Bao-Zong Wang, Peng-Cheng Hou, Youjin Deng, Kristjan Haule, Kun Chen
Summary: The study systematically investigates the fermionic sign structure in Feynman diagrams, with applications in numerical evaluation and analytical identification of dominant diagrams. By analyzing the role of symmetry in sign cancellation, it leads to significant speed improvements in diagram evaluations and reveals the relevant diagrams that dominate the dynamics.
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
Materials Science, Multidisciplinary
Maarten Van Damme, Laurens Vanderstraeten
Summary: In this study, we introduce a method based on matrix product states (MPS) to compute spectral functions of (quasi-) one-dimensional spin chains directly in momentum space. By simulating the time evolution and working with the momentum superposition of a window MPS, we can achieve accurate spectral functions with smaller entanglement growth and relatively small bond dimension. The method is applied to compute spectral lineshapes of the gapless XXZ chain and the square-lattice J1 ??? J2 Heisenberg model on a six-leg cylinder.