Proton-donor properties of water and ammonia in van der Waals complexes. Be–H2O and Be–NH3.

The potential energy surfaces (PES) of Be–H2O and Be–NH3 are studied with particular attention to characterization of proton-donor properties of water and ammonia. Calculations were performed by means of both supermolecular and intermolecular Mo\ller Plesset perturbation theory. The Be–H2O PES reveals two van der Waals minima: the C2v minimum (De=176 cm-1, Re=6.5 bohr), and the H-bonded minimum (De=161 cm-1, Re=7.5 bohr), separated by a barrier of 43 cm-1 at the T-shaped configuration. The Be–NH3 PES reveals only one van der Waals minimum, at the C3v configuration (De=260 cm-1, Re=6.5 bohr) and a saddle point at the H-bonded geometry. The locations of the minima as well as the anisotropy of the interaction are determined by the anisotropy of electric polarization contribution, embodied by the self-consistent-field (SCF)-deformation and perturbation induction energies. [ABSTRACT FROM AUTHOR]