title: Understanding and improving the efficiency of full configuration interaction quantum Monte Carlo.
abstract: Within full configuration interaction quantum Monte Carlo, we investigate how the statistical error behaves as a function of the parameters which control the stochastic sampling. We define the inefficiency as a measure of the statistical error per particle sampling the space and per time step and show there is a sizeable parameter regime where this is minimised. We find that this inefficiency increases sublinearly with Hilbert space size and can be reduced by localising the canonical Hartree-Fock molecular orbitals, suggesting that the choice of basis impacts the method beyond that of the sign problem.
authors.affiliation: Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: W A
authors.initials: WA
authors.lastname: Vigor
authors.affiliation: Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: J S
authors.initials: JS
authors.lastname: Spencer
authors.affiliation: Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: M J
authors.initials: MJ
authors.lastname: Bearpark
authors.affiliation: Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: A J W
authors.initials: AJ
authors.lastname: Thom