Stabilities and nature of the attractive interactions in HeBeO, NeBeO, and ArBeO and a comparison with analogues NGLiF, NGBN, and NGLiH (NG = He, Ar). A theoretical investigation

Results of ab initio calculations are reported for HeBeO (1), NeBeO (2), ArBeO (3), HeLiF (4), ArLiF (5), HeBN (6), ArBN (7), and HeLiH (8). At the MP2/6-31G(d,p) level, the NGBeO structures 1–3 are predicted with rather short NG-Be distances, while for 4–8 significantly longer NG-X distances are found. Dissociation into the respective noble-gas atom NG and BeO is calculated at the MP4(SDTQ)/6-31 lG(2df,2pd) level corrected by zero-point energies and basis set superposition error to be endothermic by 3.1 kcal/mol for 1, 2.2 kcal/mol for 2, and 7.0 kcal/mol for 3. For 4–8, dissociation energies D₀≤ 0.1 kcal/mol are predicted. Interactions of NG with BeO in 1–3 are investigated by analysis of the one-electron density distribution and compared with interactions between NG and Be in diatomic cations HeBeⁿ⁺, NeBeⁿ⁺, and ArBeⁿ⁺(n = 1, 2). It is concluded that the stability of NGBeO can be explained on the basis of relatively strong charge-induced dipole interactions typical of van der Waals complexes. Vibrational frequencies and infrared intensities are reported for 1–3 to aid experimental identification. For HeBeO and HeBN CASSCF geometry optimizations have additionally been performed using the 6-31G(d,p) basis set and a full-valence active space.