Electronic structure of Li 3

Abstract

Non-orthogonal single- and multi-configuration ab initio calculations have been carried out on ground-state Li 3 in its minimum-energy C 2v geometry. Their results have been compared with published work and with those of SCF, frozen-core SDCI and full-valence CI calculations. The calculations confirm the feasibility of explicit basis-set optimisation, by second-order analytical methods, for correlated wavefunctions in non-linear molecules, and compare use of optimised STO basis sets with standard, high-accuracy, GTO basis sets. The results are used as basis for a discussion of the molecule’s electronic structure. The molecule’s electron density is shown to exhibit a non-nuclear maximum, both at the SCF and frozen-core full-CI levels, and with core-correlated non-orthogonal wavefunctions. An ‘Atoms-in-Molecules’ topological analysis of the electron density shows features that may be viewed as related to the occurrence of Interstitial Orbitals in non-orthogonal electronic wavefunctions for this system. The electron density difference map (molecule minus atoms) exhibits a non-nuclear maximum at roughly the same location as the molecule’s total electron density, plus three 3p-type enrichment-depletion patterns, one centred on each nucleus. Corresponding patterns are found in Li 2. Li 3’s electric dipole and electric field gradient at the nuclei are also computed. Unexpectedly, the electric dipole value is found to exhibit significant dependence on the inclusion of inner-shell out-of-plane correlation in the wavefunction.