Further study of the BeH radical by UHF-type and configuration interaction methods

Abstract

The UHF, PUHF, EHF and CI methods have been used for calculating the isotropic and anisotropic hyperfine splitting constants and electronic energy for the BeH radical for 12 different basis sets of increasing flexibility. As the quality of the basis improves (based on an energy criterion) there is a convergence of the theoretical hyperfine splitting constants with the experimental values, except for the anisotropic h.f.s. constant for the H atom, for both the UHF and CI methods. The isotropic h.f.s. constants calculated by the EHF method converge to more positive values than observed experimentally. The EHF wavefunction is analysed in terms of a CI expansion using the EHF natural orbitals and reasons for the discrepancies are investigated.