title: Semi-stochastic full configuration interaction quantum Monte Carlo: Developments and application.
abstract: 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 present stochastic efficiencies for a variety of both molecular and lattice systems. The algorithmic details of an efficient semi-stochastic implementation are presented, with particular consideration given to the effect that the adaptation has on parallel performance in FCIQMC. We further demonstrate the benefit for calculation of reduced density matrices in FCIQMC through replica sampling, where the semi-stochastic adaptation seems to have even larger efficiency gains. We then combine these ideas to produce explicitly correlated corrected FCIQMC energies for the beryllium dimer, for which stochastic errors on the order of wavenumber accuracy are achievable.
authors.affiliation: University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: N S
authors.initials: NS
authors.lastname: Blunt
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
authors.forename: Simon D
authors.initials: SD
authors.lastname: Smart
authors.affiliation: University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: J A F
authors.initials: JA
authors.lastname: Kersten
authors.affiliation: Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: J S
authors.initials: JS
authors.lastname: Spencer
authors.affiliation: University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: George H
authors.initials: GH
authors.lastname: Booth
authors.affiliation: University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: Ali
authors.initials: A
authors.lastname: Alavi