title: Quantum Monte Carlo calculations of the dissociation energies of three-electron hemibonded radical cationic dimers.
abstract: We report variational and diffusion quantum Monte Carlo (VMC and DMC) calculations of the dissociation energies of the three-electron hemibonded radical cationic dimers of He, NH3, H2O, HF, and Ne. These systems are particularly difficult for standard density-functional methods such as the local-density approximation and the generalized gradient approximation. We have performed both all-electron (AE) and pseudopotential (PP) calculations using Slater-Jastrow wave functions with Hartree-Fock single-particle orbitals. Our results are in good agreement with coupled-cluster CCSD(T) calculations. We have also studied the relative stability of the hemibonded and hydrogen-bonded water radical dimer isomers. Our calculations indicate that the latter isomer is more stable, in agreement with post-Hartree-Fock methods. The excellent agreement between our AE and PP results demonstrates the high quality of the PPs used within our VMC and DMC calculations.
authors.affiliation: Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, J. J. Thompson Avenue, Cambridge CB3 0HE, United Kingdom. ig243@cam.ac.uk
authors.forename: I G
authors.initials: IG
authors.lastname: Gurtubay
authors.forename: N D
authors.initials: ND
authors.lastname: Drummond
authors.forename: M D
authors.initials: MD
authors.lastname: Towler
authors.forename: R J
authors.initials: RJ
authors.lastname: Needs