A study of electron affinities using the initiator approach to full configuration interaction quantum Monte Carlo.
For the atoms with Z ≤ 11, energies obtained using the "initiator" extension to full configuration interaction quantum Monte Carlo (i-FCIQMC) come to within statistical errors of the FCIQMC results. As these FCIQMC values have been shown to converge onto FCI results, the i-FCIQMC method allows similar accuracy to be achieved while significantly reducing the scaling with the size of the Slater determinant space. The i-FCIQMC electron affinities of the Z ≤ 11 atoms in the aug-cc-pVXZ basis sets are presented here. In every case, values are obtained to well within chemical accuracy [the mean absolute deviation (MAD) from the relativistically corrected experimental values is 0.41 mE(h)], and significantly improve on coupled cluster with singles, doubles and perturbative triples [CCSD(T)] results. Since the only remaining source of error is basis set incompleteness, we have investigated using CCSD(T)-F12 contributions to correct the i-FCIQMC results. By doing so, much faster convergence with respect to basis set size may be achieved for both the electron affinities and the FCIQMC ionization potentials presented in a previous paper. With this F12 correction, the MAD can be further reduced to 0.13 mE(h) for the electron affinities and 0.31 mE(h) for the ionization potentials.
Chemistry Department, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
D M
DM
Cleland
George H
GH
Booth
Ali
A
Alavi
D004583:Electrons; D006371:Helium / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D009010:Monte Carlo Method; D011789:Quantum Theory
D006371:Helium; D006859:Hydrogen