LCAO–MO–SCF Calculations Using Gaussian Basis Functions. IV. The Helium Adduct of Lithium Hydride, HeLiH

Abstract

Population analyses of wavefunctions calculated for LiH indicated that the Li-atom site was severely electron deficient, thus favoring complexing to a species with an unshared electron pair, even on a rare-gas atom. Calculations were performed for linear HeLiH as a function of HeLi distance at several fixed LiH distances. The minimum EHF in each case was found at an HeLi distance of about 4.0 bohr, and in each case the system is bound relative to the separated products He+LiH. With the HeLi distance fixed at the equilibrium position 4.0 bohr, variation of the LiH distance gave an EHF minimum at 3.05 bohr, close to the equilibrium distance of 3.015 bohr in LiH itself. The Hartree–Fock binding energy of HeLiH relative to He+LiH was estimated to be 0.092 eV. A calculation of the zero-point vibration energy of the He–Li bond indicates that HeLiH is bound by 0.08 eV with respect to dissociation along the He–Li bond. The HeLiH system appears to be intermediate between a true compound and an extremely weak van der Waals complex. The higher rare-gas complexes of LiH are expected to be more stable.