A5067933395- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Quantum, superfluid, helium dynamics
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Machine Learning in Materials Science
- Quantum many-body systems
- Quantum Computing Algorithms and Architecture
- Quantum Information and Cryptography
- Advanced Condensed Matter Physics
- Advanced NMR Techniques and Applications
- Catalytic Processes in Materials Science
- Spectroscopy and Laser Applications
- Magnetism in coordination complexes
- Catalysis and Oxidation Reactions
- Cold Atom Physics and Bose-Einstein Condensates
- Laser-Matter Interactions and Applications
- Advanced Thermodynamics and Statistical Mechanics
- Inorganic Fluorides and Related Compounds
- Photochemistry and Electron Transfer Studies
- Molecular spectroscopy and chirality
- High-pressure geophysics and materials
- Quantum Mechanics and Applications
- Strong Light-Matter Interactions
- Neural Networks and Applications
King's College London
2016-2025
Thomas Young Centre
2014-2025
University of Cambridge
2007-2020
University of Waterloo
2020
Data61
2020
Max Planck Institute for Solid State Research
2015-2020
Commonwealth Scientific and Industrial Research Organisation
2020
The Dodd-Walls Centre for Photonic and Quantum Technologies
2020
University of Iowa
2020
Massey University
2020
Python‐based simulations of chemistry framework (P y SCF) is a general‐purpose electronic structure platform designed from the ground up to emphasize code simplicity, so as facilitate new method development and enable flexible computational workflows. The package provides wide range tools support finite‐size systems, extended systems with periodic boundary conditions, low‐dimensional custom Hamiltonians, using mean‐field post‐mean‐field methods standard Gaussian basis functions. To ensure...
We have developed a new quantum Monte Carlo method for the simulation of correlated many-electron systems in full configuration-interaction (Slater determinant) spaces. The is population dynamics set walkers, and designed to simulate underlying imaginary-time Schrödinger equation interacting Hamiltonian. walkers (which carry positive or negative sign) inhabit Slater determinant space, evolve according simple rules which include spawning, death annihilation processes. show that this capable...
PySCF is a Python-based general-purpose electronic structure platform that supports first-principles simulations of molecules and solids as well accelerates the development new methodology complex computational workflows. This paper explains design philosophy behind enables it to meet these twin objectives. With several case studies, we show how users can easily implement their own methods using environment. We then summarize capabilities for molecular solid-state simulations. Finally,...
We provide a very simple adaptation of our recently published quantum Monte Carlo algorithm in full configuration-interaction (Slater determinant) spaces which dramatically reduces the number walkers required to achieve convergence. A survival criterion is imposed for newly spawned walkers. define set initiator determinants such that progeny from onto unoccupied are able survive, while not this can survive only if they already occupied. The initiators originally defined be all constructable...
The full configuration interaction quantum Monte Carlo (FCIQMC) method, as well its “initiator” extension (i-FCIQMC), is used to tackle the complex electronic structure of carbon dimer across entire dissociation reaction coordinate, a prototypical example strongly correlated molecular system. Various basis sets increasing size up large cc-pVQZ are used, spanning fully accessible N-electron over 1012 Slater determinants, and accuracy method demonstrated in each set. Convergence FCI limit...
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 newly developed stochastic technique, Full Configuration Interaction Quantum (FCIQMC), which samples exact wavefunction expanded in plane wave Slater determinants. Despite introduction of basis set incompleteness error, obtain finite-basis energy is significantly, and variationally lower than any previously published work...
We demonstrate that natural orbitals allow for reducing the computational cost of wave function based correlated calculations, especially atoms and molecules in a large box, when plane basis set under periodic boundary conditions is used. The employed are evaluated on level second-order Møller–Plesset perturbation theory (MP2), which requires effort scales as O(N5), where N measure system size. Moreover, we find simple approximation scaling to O(N4) yields similar reduction number virtual...
Using the finite simulation-cell homogeneous electron gas (HEG) as a model, we investigate convergence of correlation energy to complete basis set (CBS) limit in methods utilising plane-wave wavefunction expansions. Simple analytic and numerical results from second-order M{\o}ller-Plesset theory (MP2) suggest 1/M decay basis-set incompleteness error where M is number plane waves used calculation, allowing for straightforward extrapolation CBS limit. As shall show, choice truncation when...
For many decades, quantum chemical method development has been dominated by algorithms which involve increasingly complex series of tensor contractions over one-electron orbital spaces. Procedures for their derivation and implementation have evolved to require the minimum amount logic rely heavily on computationally efficient library-based matrix algebra optimised paging schemes. In this regard, recent exact stochastic reduce computational scaling memory overhead requires a contrasting...
We expand upon the recent semi-stochastic adaptation to full configuration interaction quantum Monte Carlo (FCIQMC). present an alternate method for generating deterministic space without a priori knowledge of wave function and stochastic efficiencies variety both molecular lattice systems. The algorithmic details efficient implementation are presented, with particular consideration given effect that has on parallel performance in FCIQMC. further demonstrate benefit calculation reduced...
A large collaboration carefully benchmarks 20 first principles many-body electronic structure methods on a test set of 7 transition metal atoms, and their ions monoxides. Good agreement is attained between the 3 systematically converged methods, resulting in experiment-free reference values. These values are used to assess accuracy modern emerging scalable approaches many-electron problem. The most accurate obtain energies indistinguishable from experimental results, with mainly limited by...
The multiconfigurational self-consistent field theory is considered the standard starting point for almost all multireference approaches required strongly correlated molecular problems. limitation of approach generally given by number orbitals in molecule, since its cost will grow exponentially with this number. We present a new approach, wherein linear determinant coefficients wave function are optimized via stochastic full configuration interaction quantum Monte Carlo technique at greatly...
We present a new approach to calculate excited states with the full configuration interaction quantum Monte Carlo (FCIQMC) method. The uses Gram-Schmidt procedure, instantaneously applied stochastically evolving distributions of walkers, orthogonalize higher energy against lower ones. It can thus be used study several lowest-energy system within same symmetry. This additional step is particularly simple and computationally inexpensive, requiring only small change underlying FCIQMC algorithm....
We present NECI, a state-of-the-art implementation of the Full Configuration Interaction Quantum Monte Carlo (FCIQMC) algorithm, method based on stochastic application Hamiltonian matrix sparse sampling wave function. The program utilizes very powerful parallelization and scales efficiently to more than 24 000 central processing unit cores. In this paper, we describe core functionalities NECI its recent developments. This includes capabilities calculate ground excited state energies,...
We derive a widely applicable first-principles approach for determining two-body, static effective interactions low-energy Hamiltonians with quantitative accuracy. The algebraic construction rigorously conserves all instantaneous two-point correlation functions in chosen model space at the level of random phase approximation, improving upon traditional uncontrolled approximations. Applied to screened within quantum embedding framework, we demonstrate these faithfully describe relaxation...
A new quantum Monte Carlo (QMC) method is used to calculate exact, full configuration-interaction (FCI) energies of the neutral and cationic elements from Li Mg, in a family commonly basis sets. Annihilation processes between positive negative walkers enable exact N-electron wave function emerge as linear superposition (factorially large) space Slater determinants, with individual determinants being stochastically sampled. As result, extremely large spaces (exceeding 10(15) determinants)...
For the atoms with Z ⩽ 11, energies obtained using “initiator” extension to full configuration interaction quantum Monte Carlo (i-FCIQMC) come within statistical errors of FCIQMC results. As these values have been shown converge onto FCI results, i-FCIQMC method allows similar accuracy be achieved while significantly reducing scaling size Slater determinant space. The electron affinities 11 in aug-cc-pVXZ basis sets are presented here. In every case, well chemical [the mean absolute...
Using the homogeneous electron gas (HEG) as a model, we investigate sources of error in "initiator" adaptation to full configuration interaction quantum Monte Carlo (i-FCIQMC), with view accelerating convergence. In particular, find that fixed-shift phase, where walker number is allowed grow slowly, can be used effectively assess stochastic and initiator error. this approach provide simple explanations for internal parameters an i-FCIQMC simulation. We exploit consistent basis sets...
Properties that are necessarily formulated within pure (symmetric) expectation values difficult to calculate for projector quantum Monte Carlo approaches, but critical in order compute many of the important observable properties electronic systems. Here, we investigate an approach sampling unbiased reduced density matrices Full Configuration Interaction Quantum dynamic, which requires only small computational overheads. This is achieved via independent replica population walkers sampled...
The initiator full configuration interaction quantum Monte Carlo (i-FCIQMC) method has recently been developed as a highly accurate stochastic electronic structure technique. It shown to calculate the exact basis-set ground state energy of small molecules, within modest error bars, using tractable computational cost. Here, we use this technique elucidate an often troublesome series first-row diatomics consisting Be2, C2, CN, CO, N2, NO, O2, and F2. Using i-FCIQMC, dissociation energies these...
We present an approach to the calculation of arbitrary spectral, thermal, and excited state properties within full configuration interaction quzantum Monte Carlo framework. This is achieved via unbiased projection Hamiltonian eigenvalue problem into a space stochastically sampled Krylov vectors, thus, enabling real-frequency spectral thermal avoiding explicit analytic continuation. use this calculate temperature-dependent one- two-body functions for various Hubbard models, as well isolated...
We present a simple, robust, and black-box approach to the implementation use of local, periodic, atom-centered Gaussian basis functions within plane wave code, in computationally efficient manner. The procedure outlined is based on representation Gaussians finite bandwidth by their underlying coefficients. core region handled projected augment framework, pseudizing cutoff radius around each nucleus, smoothing so that they are faithfully represented with only moderate kinetic energy cutoff....
We investigate fully self-consistent multiscale quantum-classical algorithms on current generation superconducting quantum computers, in a unified approach to tackle the correlated electronic structure of large systems both chemistry and condensed matter physics. In these contexts, strongly region extended system is isolated self-consistently coupled its environment via sampling reduced density matrices. analyze viability devices provide required fidelity objects for robust efficient...