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We extend the scope of full configuration interaction quantum Monte Carlo (FCIQMC) to be applied to coupled fermion-boson hamiltonians, alleviating the a priori truncation in boson occupation which is necessary for many other wave function…

Strongly Correlated Electrons · Physics 2022-11-09 Robert J. Anderson , Charles C. J. Scott , George H. Booth

By performing a stochastic dynamic in a space of Slater determinants, the Full Configuration Interaction Quantum Monte Carlo (FCIQMC) method has been able to obtain energies which are essentially free from systematic error to the basis set…

Computational Physics · Physics 2014-10-10 George H. Booth , Deidre Cleland , Ali Alavi , David P. Tew

We investigate the sign problem for full configuration interaction quantum Monte Carlo (FCIQMC), a stochastic algorithm for finding the ground state solution of the Schr\"odinger equation with substantially reduced computational cost…

Computational Physics · Physics 2014-11-05 James J. Shepherd , Gustavo E. Scuseria , James S. Spencer

We expand upon the recent semi-stochastic adaptation to full configuration interaction quantum Monte Carlo (FCIQMC). We present an alternate method for generating the deterministic space without a priori knowledge of the wave function and…

Computational Physics · Physics 2015-11-17 N. S. Blunt , Simon D. Smart , J. A. F. Kersten , J. S. Spencer , George H. Booth , Ali Alavi

In this paper, we propose a general analysis framework for inexact power iteration, which can be used to efficiently solve high dimensional eigenvalue problems arising from quantum many-body problems. Under the proposed framework, we…

Numerical Analysis · Mathematics 2018-06-29 Jianfeng Lu , Zhe Wang

Building on the success of Quantum Monte Carlo techniques such as diffusion Monte Carlo, alternative stochastic approaches to solve electronic structure problems have emerged over the last decade. The full configuration interaction quantum…

An adaptation of the full configuration interaction quantum Monte Carlo (FCIQMC) method is presented, for correlated electron problems containing heavy elements and the presence of significant relativistic effects. The modified algorithm…

Chemical Physics · Physics 2020-10-26 Robert J. Anderson , George H. Booth

Using the homogeneous electron gas (HEG) as a model, we investigate the sources of error in the `initiator' adaptation to Full Configuration Interaction Quantum Monte Carlo (i-FCIQMC), with a view to accelerating convergence. In particular…

Computational Physics · Physics 2012-06-26 James J. Shepherd , George H. Booth , Ali Alavi

The Full Configuration Interaction Quantum Monte Carlo (FCIQMC) method has proved able to provide near-exact solutions to the electronic Schr\"odinger equation within a finite orbital basis set, without relying on an expansion about a…

Computational Physics · Physics 2016-08-24 Jennifer Kersten , George H. Booth , Ali Alavi

Auxiliary Field Quantum Monte Carlo (AFQMC) has emerged as a powerful framework for treating strongly correlated electronic systems, offering a favorable balance between computational cost and accuracy. In this paper, we present a novel…

Chemical Physics · Physics 2026-04-03 Maxine Luo , Victor Chen , Yu Wang , Christian B. Mendl

Highly accurate results for the homogeneous electron gas (HEG) have only been achieved to date within a diffusion Monte Carlo (DMC) framework. Here, we introduce a newly developed stochastic technique, Full Configuration Interaction Quantum…

Quantum Gases · Physics 2012-02-22 James J. Shepherd , George Booth , Andreas Grüneis , Ali Alavi

Full configuration interaction quantum Monte Carlo (FCIQMC) is a state-of-the-art stochastic electronic structure method, providing a methodology to compute FCI-level state energies of molecular systems within a quantum chemical basis.…

Chemical Physics · Physics 2022-04-29 Tonghuan Jiang , Wei Fang , Ali Alavi , Ji Chen

We here apply the recently developed initiator density matrix quantum Monte Carlo (i-DMQMC) to a wide range of chemical environments using atoms and molecules in vacuum. i-DMQMC samples the exact density matrix of a Hamiltonian at finite…

Chemical Physics · Physics 2019-12-03 Hayley R. Petras , Sai Kumar Ramadugu , Fionn D. Malone , James J. Shepherd

Accurate ab initio calculations of 3d transition metal monoxide molecules have attracted extensive attention because of its relevance in physical and chemical science, as well as theoretical challenges in treating strong electron…

Strongly Correlated Electrons · Physics 2021-11-02 Tonghuan Jiang , Yilin Chen , Nikolay Bogdanov , Enge Wang , Ali Alavi , Ji Chen

The convergence of full configuration interaction quantum Monte Carlo (FCIQMC) is accelerated using a quasi-Newton propagation (QN) which can also be applied to coupled cluster Monte Carlo (CCMC). The computational scaling of this optimised…

Chemical Physics · Physics 2020-06-11 Verena A. Neufeld , Alex J. W. Thom

We present a quantum-in-quantum embedding strategy coupled to machine learning potentials to improve on the accuracy of quantum-classical hybrid models for the description of large molecules. In such hybrid models, relevant structural…

Full Configuration Interaction Quantum Monte Carlo (FCIQMC) has been effectively applied to very large configuration interaction (CI) problems, and was recently adapted for use as an active space solver and combined with orbital…

Chemical Physics · Physics 2020-02-19 Robert J. Anderson , Toru Shiozaki , George H. Booth

We suggest an efficient method to resolve electronic cusps in electronic structure calculations by using an effective transcorrelated Hamiltonian. This effective Hamiltonian takes a simple form for plane wave bases, containing up to…

Computational Physics · Physics 2018-02-14 Hongjun Luo , Ali Alavi

Quantum Monte Carlo (QMC) is an advanced simulation methodology for studies of manybody quantum systems. In this review, we focus on the electronic structure QMC, i.e., methods relevant for systems described by the electron-ion…

Other Condensed Matter · Physics 2010-08-16 Michal Bajdich , Lubos Mitas

We present a perturbative correction within initiator full configuration interaction quantum Monte Carlo (i-FCIQMC). In the existing i-FCIQMC algorithm, a significant number of spawned walkers are discarded due to the initiator criteria.…

Chemical Physics · Physics 2018-06-13 Nick S. Blunt
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