Article
Chemistry, Physical
Xiang Li, Jia-Cheng Huang, Guang-Ze Zhang, Hao-En Li, Chang-Su Cao, Dingshun Lv, Han-Shi Hu
Summary: This article introduces a general nonstochastic optimization algorithm for neural-network quantum states (NQS) in chemical systems. The algorithm accelerates the optimization process by bypassing the need for Markov-chain Monte Carlo within the variational Monte Carlo (VMC) framework, and it offers comparable or superior accuracy and convergence compared to its stochastic counterpart.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Chemistry, Physical
Janus J. Eriksen
Summary: The Perspective discusses the future prospects of full configuration interaction (FCI) theory, comparing key contemporary approximations and discussing their required traits. Despite significant progress in the field over the years, there is still a need to enhance the overall applicability of electronic structure theory for systems of general composition and increasing size.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Nick S. Blunt
Summary: This study investigates fixed- and partial-node approximations in Slater determinant basis sets using FCIQMC for sampling. While the partial-node approximation is limited due to the large walker populations required, the fixed-node approximation proves to be an accurate and practical method, particularly for CAS problems in large active spaces.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Chemistry, Physical
Jean-Paul Malrieu, Jean-Louis Heully
Summary: The present paper reformulates and improves a determinant-based second-order multi-reference perturbative formalism, taking into account the interactions between repeated determinants in outer space through modification of the energy denominators. The paper shows that size-consistency can be achieved even when the model space is not a complete active space, as long as the zero-order function satisfies certain conditions. The method's physical content is illustrated through model problems, highlighting its robustness and the flexibility to revise the model-space component of the wave function.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Computer Science, Software Engineering
Zackary Misso, Benedikt Bitterli, Iliyan Georgiev, Wojciech Jarosz
Summary: We introduce a general framework for transforming biased estimators into unbiased and consistent estimators in the same field. We demonstrate how this framework can be applied to rendering and improve existing unbiased estimation strategies. We provide examples of novel unbiased forms of transmittance estimation, photon mapping, and finite differences that are developed using this framework.
ACM TRANSACTIONS ON GRAPHICS
(2022)
Review
Chemistry, Physical
Yihe Xu, Yifan Cheng, Yinxuan Song, Haibo Ma
Summary: Thanks to the high compression of the matrix product state (MPS) form and the efficient site-by-site iterative sweeping optimization algorithm, the density matrix normalization group (DMRG) and its time-dependent variant (TD-DMRG) have become powerful computational tools for accurately simulating the electronic structure and quantum dynamics of strongly correlated molecules. However, to understand the quantum many-body behaviors of realistic systems, the interaction between the active subsystem and the correlated environment needs to be considered. Three new post-DMRG and TD-DMRG approaches are introduced in this paper to extend the efficacy of accurate DMRG/TD-DMRG computations to realistic strongly correlated systems coupled with large environments.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Engineering, Multidisciplinary
M. Croci, K. E. Willcox, S. J. Wright
Summary: This paper extends MLBLUE method to multi-output forward UQ problems and presents new semidefinite programming formulations for their optimal setup. These formulations yield the optimal number of samples required and the optimal selection of low-fidelity models to use. The new multi-output formulations can be solved reliably and efficiently.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Mathematics, Applied
Zhijian He, Zhenghang Xu, Xiaoqun Wang
Summary: This paper proposes a new variational Bayes algorithm based on multilevel Monte Carlo and randomized quasi-Monte Carlo sampling, for handling inference problems with intractable likelihood functions. Compared to existing algorithms, this algorithm has better performance and convergence rate.
SIAM JOURNAL ON SCIENTIFIC COMPUTING
(2022)
Article
Chemistry, Physical
Jorge Alfonso Charry Martinez, Matteo Barborini, Alexandre Tkatchenko
Summary: The article introduces an accurate, efficient, and transferable variational ansatz based on a combination of electron-positron geminal orbitals and a Jastrow factor. This ansatz explicitly includes the electron-positron correlations and is optimized using variational Monte Carlo. The approach is applied to calculate binding energies for various atomic and molecular systems, showing improved accuracy compared to previous calculations.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)
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)
Review
Chemistry, Multidisciplinary
Janus J. Eriksen, Juergen Gauss
Summary: The recent many-body expanded full configuration interaction (MBE-FCI) method is critically assessed, with a discussion on its advantages, drawbacks, history, future research directions, and recent applications.
WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE
(2021)
Article
Physics, Particles & Fields
Jeppe R. Andersen, Andreas Maier
Summary: We propose a novel method for eliminating negative Monte Carlo event weights that is independent of any specific data analysis and preserves all physical observables. Using predictions for the production of a W boson with two jets calculated at the next-to-leading order perturbation theory, we demonstrate the overall performance and systematic improvement with increasing event sample size.
EUROPEAN PHYSICAL JOURNAL C
(2022)
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
Multidisciplinary Sciences
Javier Robledo Moreno, Giuseppe Carleo, Antoine Georges, James Stokes
Summary: We introduce a new family of variational wave functions for simulating strongly correlated fermionic systems. By incorporating hidden additional degrees of freedom and optimizing the constraint and single-particle orbitals using a neural network parameterization, our construction overcomes limitations of hidden-particle representations and is proven to be universal. Applied to the ground-state properties of the Hubbard model, our approach achieves competitive levels of accuracy with state-of-the-art variational methods.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
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
Chemistry, Physical
Tina N. Mihm, Bingdi Yang, James J. Shepherd
Summary: Calculations using coupled cluster on solids have sparked a debate on using a N-1/3 power law for fitting correlation energy when extrapolating to the thermodynamic limit, as opposed to the more commonly used N-1 power law. While N-1/3 power law seems to fit better for large system sizes, analysis suggests that N-1 power law still applies to large systems, with N-1/3 power law occurring only at low N values.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Chemistry, Physical
William Z. van Benschoten, James J. Shepherd
Summary: The density matrix quantum Monte Carlo (DMQMC) method stochastically samples the exact N-body density matrix for interacting electrons at finite temperature. We introduce a simple modification to the interaction picture DMQMC (IP-DMQMC) method that allows for the sampling of a temperature range within a single calculation, reducing the computational cost.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Laura Weiler, Tina N. Mihm, James J. Shepherd
Summary: This article introduces a Gaussian process regression model for the transition structure factor in metal periodic coupled cluster singles and doubles calculations. The model is inspired by previous methods and uses a one-dimensional function to fit the structure factor and correct for finite size errors.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Multidisciplinary Sciences
T. M. Graham, Y. Song, J. Scott, C. Poole, L. Phuttitarn, K. Jooya, P. Eichler, X. Jiang, A. Marra, B. Grinkemeyer, M. Kwon, M. Ebert, J. Cherek, M. T. Lichtman, M. Gillette, J. Gilbert, D. Bowman, T. Ballance, C. Campbell, E. D. Dahl, O. Crawford, N. S. Blunt, B. Rogers, T. Noel, M. Saffman
Summary: Gate-model quantum computers promise to solve computational problems by utilizing neutral-atom hyperfine qubits and strong entangling interactions provided by Rydberg states. Several quantum algorithms have been successfully demonstrated on a programmable neutral-atom quantum computer.
Article
Chemistry, Multidisciplinary
Robert Izsak, Christoph Riplinger, Nick S. Blunt, Bernardo de Souza, Nicole Holzmann, Ophelia Crawford, Joan Camps, Frank Neese, Patrick Schopf
Summary: Quantum computers are expected to be useful in simulating strongly correlated chemical systems, but careful selection of orbital spaces is crucial. This study presents a scheme for automatically selecting an active space and combines quantum phase estimation and variational quantum eigensolver algorithms to accurately describe the environment. The protocol outlined here can be applied to chemical systems of any size, including those beyond the capabilities of classical computation.
JOURNAL OF COMPUTATIONAL CHEMISTRY
(2023)
Review
Physics, Multidisciplinary
Jules Tilly, Hongxiang Chen, Shuxiang Cao, Dario Picozzi, Kanav Setia, Ying Li, Edward Grant, Leonard Wossnig, Ivan Rungger, George H. Booth, Jonathan Tennyson
Summary: The variational quantum eigensolver (VQE) is a method used to compute the ground state energy of a Hamiltonian, which is important in quantum chemistry and condensed matter physics. It has the advantage of being able to model complex wavefunctions in polynomial time, making it a promising application for quantum computing. However, there are still many open questions regarding optimization, quantum noise, and other challenges, which require further research and exploration.
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS
(2022)
Article
Chemistry, Physical
Nick S. Blunt, Joan Camps, Ophelia Crawford, Robert Izsak, Sebastian Leontica, Arjun Mirani, Alexandra E. Moylett, Sam A. Scivier, Christoph Sunderhauf, Patrick Schopf, Jacob M. Taylor, Nicole Holzmann
Summary: Computational chemistry is crucial for the pharmaceutical industry, and quantum computing is a rapidly advancing technology that promises to revolutionize computational capabilities in chemical research. This article explores the potential applications of quantum computation in pharmaceutical problems, specifically in simulating molecules. The authors provide estimates of the quantum computational cost for simulating a protein-drug complex and highlight recent advancements in quantum algorithms that significantly reduce the required resources.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)
Article
Chemistry, Physical
William Z. Van Benschoten, Laura Weiler, Gabriel J. Smith, Songhang Man, Taylor DeMello, James J. Shepherd
Summary: We propose a machine learning approach to calculate electronic specific heat capacities for various benchmark molecular systems. Our models are based on data from density matrix quantum Monte Carlo, which can compute the electronic energy at finite temperature. We utilize Gaussian process regression to model the energy and analytical derivatives to obtain the specific heat capacity. Additionally, we calculate the entropy using numerical integration. Comparisons with cubic splines and finite differences are made on molecular systems where exact diagonalization is feasible, and further comparisons with approximate methods are performed on larger molecules.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Tina N. Mihm, Laura Weiler, James J. Shepherd
Summary: This study reveals, for the first time, the contribution mechanisms of Ferroin compounds Fe(CN)3(4e) and Fe(CN)4(2e) to the spectra through analysis of vibrational dynamics and from the perspective of polarized spectra. It is found that the contributions of Fe(CN)3(4e) and Fe(CN)4(2e) exhibit different characteristics in spectral analysis, providing a more comprehensive theoretical understanding.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Chemistry, Physical
Robert Izsak, Aleksei V. Ivanov, Nick S. Blunt, Nicole Holzmann, Frank Neese
Summary: In this article, the different measures of electron correlation in wave function theory, density functional theory, and quantum information theory are briefly reviewed. The focus is then placed on a more traditional metric based on dominant weights in the full configuration solution and its behavior regarding the choice of N-electron and one-electron basis. The impact of symmetry is discussed, and the usefulness of distinguishing between determinants, configuration state functions, and configurations as reference functions is emphasized.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Polymer Science
Arjun Paudel, Emily J. Campbell, William Z. Van Benschoten, Grant W. Otting, James J. Shepherd, Ned B. Bowden
Summary: A series of polymers with a backbone of alternating nitrogen and sulfur single bonds were synthesized for the first time. These polymers were based on polythiazyl (SN)x, which exhibited electrical conductivity at room temperature and superconductivity at low temperatures in the absence of doping. The polymers were synthesized using the reaction between sulfur dichloride (SCl2) and either anilines or octylamine. The polymers showed red color and had molecular weights ranging from 6,200 to 35,000 g mol-1.
Article
Chemistry, Physical
William Z. Van Benschoten, Hayley R. Petras, James J. Shepherd
Summary: In this study, full configuration interaction and density matrix quantum Monte Carlo methods are used to calculate the electronic free energy surface of the nitrogen dimer within the free-energy Born-Oppenheimer approximation. We observe a temperature regime where the internal energy enhances bond strength and entropy contributions gradually weaken the bond with increasing temperature. The thermally driven dissociation of the nitrogen dimer is predicted to occur between 22,000 and 63,200 K depending on symmetries and basis set, with inclusion of more spatial and spin symmetries reducing the required temperature. The structure of the density matrix at various temperatures and bond lengths is explored to understand the origin of these observations.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Physics, Multidisciplinary
Yannic Rath, George H. Booth
Summary: This paper introduces a quantum Gaussian process state, which is obtained by statistically inferring the wave function supported by a dataset of unentangled product states. The state can be condensed into a compact and expressive parametric form, and it shows competitive or superior variational flexibility compared to established alternatives.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Computer Science, Interdisciplinary Applications
Tina N. Mihm, Tobias Schafer, Sai Kumar Ramadugu, Laura Weiler, Andreas Gruneis, James J. Shepherd
Summary: Efficient and accurate quantum mechanical approximations are crucial for computational materials science, with coupled cluster theory showing potential for widespread adoption. A study has found that by using the transition structure factor to identify a specific twist angle, computational time can be significantly reduced with applicability across a broader range of materials.
NATURE COMPUTATIONAL SCIENCE
(2021)
