On the structure and physical origin of the interaction between lithium and acetylene molecule

Abstract

The supermolecular UHF coupled-clusters method was used to investigate the energetics of the weak interaction of rigid acetylene molecule with lithium atom. The obtained potential energy surface (PES) corrected on the basis set superposition error indicate the strong interaction for the perpendicular orientation at R =2.59 Å with a well depth of D e =1716 μ E h . The presented PES reveals also the second minimum for the linear orientation at R =5.85 Å with a well depth of D e =349 μ E h . The zero point correction is negligible. The physical origin of stability of localised structures was analysed by the intermolecular perturbation theory based on the single determinant UHF wave function. The separation of the interaction energy shows that the positions of the predicted stable structures (at R =2.59 Å) are primarily determined by the attractive components included in HF deformation and dispersion energies.