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Dive into the research topics where Fionn D. Malone is active.

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Featured researches published by Fionn D. Malone.


Journal of Chemical Physics | 2015

Interaction picture density matrix quantum Monte Carlo

Fionn D. Malone; N. S. Blunt; James J. Shepherd; Derek K. K. Lee; J. S. Spencer; W. M. C. Foulkes

The recently developed density matrix quantum Monte Carlo (DMQMC) algorithm stochastically samples the N-body thermal density matrix and hence provides access to exact properties of many-particle quantum systems at arbitrary temperatures. We demonstrate that moving to the interaction picture provides substantial benefits when applying DMQMC to interacting fermions. In this first study, we focus on a system of much recent interest: the uniform electron gas in the warm dense regime. The basis set incompleteness error at finite temperature is investigated and extrapolated via a simple Monte Carlo sampling procedure. Finally, we provide benchmark calculations for a four-electron system, comparing our results to previous work where possible.


Physics of Plasmas | 2017

Ab initio quantum Monte Carlo simulation of the warm dense electron gas

Tobias Dornheim; Simon Groth; Fionn D. Malone; T. Schoof; Travis Sjostrom; W. M. C. Foulkes; M. Bonitz

Warm dense matter is one of the most active frontiers in plasma physics due to its relevance for dense astrophysical objects and for novel laboratory experiments in which matter is being strongly compressed, e.g., by high-power lasers. Its description is theoretically very challenging as it contains correlated quantum electrons at finite temperature—a system that cannot be accurately modeled by standard analytical or ground state approaches. Recently, several breakthroughs have been achieved in the field of fermionic quantum Monte Carlo simulations. First, it was shown that exact simulations of a finite model system ( 30…100 electrons) are possible, which avoid any simplifying approximations such as fixed nodes [Schoof et al., Phys. Rev. Lett. 115, 130402 (2015)]. Second, a novel way to accurately extrapolate these results to the thermodynamic limit was reported by Dornheim et al. [Phys. Rev. Lett. 117, 156403 (2016)]. As a result, now thermodynamic results for the warm dense electron gas are available, w...


Journal of open research software | 2015

Open-Source Development Experiences in Scientific Software: The HANDE Quantum Monte Carlo Project

J. S. Spencer; N. S. Blunt; W. A. Vigor; Fionn D. Malone; W. M. C. Foulkes; James J. Shepherd; Alex J. W. Thom

J. S. Spencer, 2, ∗ N. S. Blunt, W. A. Vigor, F. D. Malone, W. M. C. Foulkes, James J. Shepherd, and A. J. W. Thom ∗ Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom Department of Physics, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom University Chemical Laboratory, Lensfield Road, Cambridge, CB2 1EW, United Kingdom Department of Chemistry, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom Department of Chemistry, Rice University, Houston, TX 77005-1892, USA (Dated: July 22, 2014)


Journal of Physics: Condensed Matter | 2018

QMCPACK: An open source ab initio quantum Monte Carlo package for the electronic structure of atoms, molecules and solids

Jeongnim Kim; Andrew David Baczewski; Todd D Beaudet; Anouar Benali; M. Chandler Bennett; M. Berrill; N. S. Blunt; Edgar Josué Landinez Borda; Michele Casula; David M. Ceperley; Simone Chiesa; Bryan K. Clark; Raymond Clay; Kris T. Delaney; Mark Douglas Dewing; Kenneth Esler; Hongxia Hao; Olle Heinonen; Paul R. C. Kent; Jaron T. Krogel; Ilkka Kylänpää; Ying Wai Li; M. Graham Lopez; Ye Luo; Fionn D. Malone; Richard M. Martin; Amrita Mathuriya; Jeremy McMinis; Cody Melton; Lubos Mitas

QMCPACK is an open source quantum Monte Carlo package for ab initio electronic structure calculations. It supports calculations of metallic and insulating solids, molecules, atoms, and some model Hamiltonians. Implemented real space quantum Monte Carlo algorithms include variational, diffusion, and reptation Monte Carlo. QMCPACK uses Slater-Jastrow type trial wavefunctions in conjunction with a sophisticated optimizer capable of optimizing tens of thousands of parameters. The orbital space auxiliary-field quantum Monte Carlo method is also implemented, enabling cross validation between different highly accurate methods. The code is specifically optimized for calculations with large numbers of electrons on the latest high performance computing architectures, including multicore central processing unit and graphical processing unit systems. We detail the programs capabilities, outline its structure, and give examples of its use in current research calculations. The package is available at http://qmcpack.org.


Journal of Chemical Physics | 2018

Auxiliary-field quantum Monte Carlo calculations of the structural properties of nickel oxide

Shuai Zhang; Fionn D. Malone; Miguel Morales

Auxiliary-field quantum Monte Carlo (AFQMC) has repeatedly demonstrated itself as one of the most accurate quantum many-body methods, capable of simulating both real and model systems. In this article, we investigate the application of AFQMC to realistic strongly correlated materials in periodic Gaussian basis sets. Using nickel oxide (NiO) as an example, we investigate the importance of finite size effects and basis set errors on the structural properties of the correlated solid. We provide benchmark calculations for NiO and compare our results to both experimental measurements and existing theoretical methods.


Physical Review Letters | 2016

Ab Initio Quantum Monte Carlo Simulation of the Warm Dense Electron Gas in the Thermodynamic Limit.

Tobias Dornheim; Simon Groth; Travis Sjostrom; Fionn D. Malone; W. M. C. Foulkes; M. Bonitz


Physical Review Letters | 2017

Ab initio exchange-correlation free energy of the uniform electron gas at warm dense matter conditions

Simon Groth; Tobias Dornheim; Travis Sjostrom; Fionn D. Malone; W. M. C. Foulkes; M. Bonitz


Physical Review Letters | 2016

Accurate exchange-correlation energies for the warm dense electron gas

Fionn D. Malone; N. S. Blunt; Ethan W. Brown; Derek K. K. Lee; J. S. Spencer; W. M. C. Foulkes; James J. Shepherd


Science and Engineering Ethics | 2014

The Highly Accurate N-DEterminant (HANDE) quantum Monte Carlo project: Open-source stochastic diagonalisation for quantum chemistry

J. S. Spencer; N. S. Blunt; W. A. Vigor; Fionn D. Malone; W. M. C. Foulkes; James J. Shepherd; Alex J. W. Thom


arXiv: Chemical Physics | 2018

Overcoming the Memory Bottleneck in Auxiliary Field Quantum Monte Carlo Simulations with Interpolative Separable Density Fitting

Fionn D. Malone; Shuai Zhang; Miguel Morales

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N. S. Blunt

University of Cambridge

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Shuai Zhang

Lawrence Livermore National Laboratory

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James J. Shepherd

Massachusetts Institute of Technology

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Miguel Morales

Lawrence Livermore National Laboratory

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Travis Sjostrom

Los Alamos National Laboratory

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