title: Developments in stochastic coupled cluster theory: The initiator approximation and application to the uniform electron gas.
abstract: We describe further details of the stochastic coupled cluster method and a diagnostic of such calculations, the shoulder height, akin to the plateau found in full configuration interaction quantum Monte Carlo. We describe an initiator modification to stochastic coupled cluster theory and show that initiator calculations can at times be extrapolated to the unbiased limit. We apply this method to the 3D 14-electron uniform electron gas and present complete basis set limit values of the coupled cluster singles and doubles (CCSD) and previously unattainable coupled cluster singles and doubles with perturbative triples (CCSDT) correlation energies for up to r(s) = 2, showing a requirement to include triple excitations to accurately calculate energies at high densities.
authors.affiliation: Department of Physics and Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: James S
authors.initials: JS
authors.lastname: Spencer
authors.affiliation: University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, United Kingdom and Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: Alex J W
authors.initials: AJ
authors.lastname: Thom