# HANDE

HANDE is an open-source software package for stochastic quantum chemistry under active development, run by a non-profit community of UK academics headed by Dr James Spencer (Imperial College London) and Dr Alex Thom (University of Cambridge).

HANDE contains highly scalable implementations of the full configuration interaction quantum Monte Carlo [1] and coupled cluster Monte Carlo [2] methods including the initiator approximation [3] and semi-stochastic approach [4], as well as the density matrix quantum Monte Carlo method [5]. HANDE can treat a variety of quantum systems, including molecular systems (via integrals obtained from a quantum chemistry package) and the uniform electron gas as well as the Hubbard and Heisenberg models.

HANDE version 1.0 can be obtained from https://github.com/hande-qmc/hande.

For any questions on using and/or developing HANDE, please contact James or Alex in the first instance:

## HANDE development team

Code, theory, applications, etc:

- James Spencer (Imperial College London)
- Alex Thom (University of Cambridge)
- Nick Blunt (University of Cambridge)
- Fionn Malone (Imperial College London)
- Ruth Franklin (University of Cambridge)
- Charlie Scott (University of Cambridge)
- Verena Neufeld (University of Cambridge)
- William Vigor (Imperial College London)
- James Shepherd (MIT)
- Matthew Foulkes (Imperial College London)

Past contributors:

- Thomas Rogers (Imperial College London)
- Will Handley (University of Cambridge)
- Joseph Weston (Imperial College London)

## Publications

F.D. Malone, N.S. Blunt, E.W. Brown, D.K.K. Lee, J.S. Spencer, W.M.C. Foulkes, J.J. Shepherd. Accurate exchange-correlation energies for the warm dense electron gas, arXiv:1602.05104 [cond-mat.str-el].

J.J. Shepherd, T.M. Henderson, G.E. Scuseria. Using full configuration interaction quantum Monte Carlo in a seniority zero space to investigate the correlation energy equivalence of pair coupled cluster doubles and doubly occupied configuration interaction, J. Chem. Phys. 144, 094112 (2016).

W.A. Vigor, J.S. Spencer, M.J. Bearpark, A.J.W. Thom. Understanding and improving the efficiency of full configuration interaction quantum Monte Carlo, J. Chem. Phys. 144, 094110 (2016).

J.S. Spencer, A.J.W. Thom. Developments in stochastic coupled cluster theory: The initiator approximation and application to the uniform electron gas, J. Chem. Phys. 144, 084108 (2016).

R.S.T. Franklin, J.S. Spencer, A. Zoccante, A.J.W. Thom. Linked coupled cluster Monte Carlo, J Chem. Phys. 144, 044111 (2016).

J.S. Spencer, N.S. Blunt, W.A. Vigor, F.D. Malone, W.M.C. Foulkes, J.J. Shepherd, A.J.W. Thom. Open-Source Development Experiences in Scientific Software: The HANDE Quantum Monte Carlo Project, J. Open Research Software 3(1), 9 (2015).

W.A. Vigor, J.S. Spencer, M.J. Bearpark, A.J.W. Thom. Minimising biases in full configuration interaction quantum Monte Carlo, J. Chem. Phys. 142, 104101 (2015).

F.D. Malone, N.S. Blunt, J.J. Shepherd, D.K.K. Lee, J.S. Spencer, W.M.C. Foulkes. Interaction picture density matrix quantum Monte Carlo, J. Chem. Phys. 143, 044116 (2015).

J.J. Shepherd, G.E. Scuseria, J.S. Spencer. Sign problem in full configuration interaction quantum Monte Carlo: Linear and sublinear representation regimes for the exact wave function, Phys. Rev. B 90, 155130 (2014).

N.S. Blunt, T.W. Rogers, J.S. Spencer, W.M.C. Foulkes. Density-matrix quantum Monte Carlo method, Phys. Rev. B, 89, 245124 (2014).

J.S. Spencer, N.S. Blunt, W.M.C. Foulkes. The sign problem and population dynamics in the full configuration interaction quantum Monte Carlo method, J. Chem. Phys. 136, 054110 (2012).

## Funding

Our team receives funding from EPSRC, the Royal Society, and the Royal Commission for the Exhibition of 1851. We are also grateful for a research environment provided by the Thomas Young Centre.

## References

[1] | Fermion Monte Carlo without fixed nodes a game of life, death, and annihilation in Slater determinant space, G.H. Booth, A.J.W. Thom, A. Alavi, J. Chem. Phys., 131 054106 (2009). |

[2] | Stochastic Coupled Cluster Theory, A.J.W. Thom, Phys. Rev. Lett. 105, 263004 (2010). |

[3] | Survival of the Fittest: Accelerating Convergence in Full Configuration-Interaction Quantum Monte Carlo , D. Cleland, G.H. Booth, A. Alavi, J. Chem. Phys., 132, 041103 (2010). |

[4] | Semistochastic Projector Monte Carlo Method. F. Petruzielo, A. Holmes, H. Changlani, M. Nightingale, C. Umrigar, Phys. Rev. Lett. 109, 230201 (2012). |

[5] | Density-matrix quantum Monte Carlo method. N.S. Blunt, T. W. Rogers, J. S. Spencer, and W. M. C. Foulkes, Phys. Rev. B, 89, 245124 (2014). |