Accuracy of energy-adjusted quasirelativistic pseudopotentials: a calibration study of XH and X₂ (X = F, Cl, Br, I, At)

Abstract

Quasirelativistic pseudopotential calibration calculations have been performed for the halogen monohydrides XH and homonuclear dimers X₂ (X = F, Cl, Br, I, At) using large uncontracted basis sets at various levels of theory: self-consistent field calculations with subsequent single-reference coupled-cluster singles and doubles calculations including a perturbative estimate for the contribution of triples as well as multi-configuration self-consistent field calculations with subsequent multi-reference averaged coupled-pair functional calculations. Spin-orbit contributions were derived from singles and doubles configuration interaction studies. The pseudopotential results are compared with scalar relativistic self-consistent field all-electron calculations using the Douglas-Kroll-Hess Hamiltonian as well as with experimental data. The accuracy of the pseudopotential-derived molecular constants in comparison with all-electron (experimental) data is better than 0·018 (0·010) Å for bond lengths, 26 (34) cm⁻¹ for vibrational constants and 0·04 (0·20) eV for binding energies. Predictions for the properties of the astatine compounds HAt and At₂ are made.