HIGHLY ACCURATE ESTIMATES OF HYDROGEN-BOND ENERGIES RELYING ON BASIS-SET CONVERGENCE PATTERNS

We introduce a method for the determination of highly accurate estimat es of the electronic interaction energies in uncharged hydrogen-bonded clusters, using basis set convergence patterns (=BSCP) of the aug-cc- pVxZ series of basis sets at MP2(FC) level of theory. The method is ch aracterized by its robustness toward systematic deficiencies of MP2(FC )/aug-cc-pVxZ description of hydrogen bonds. The achieved reliability is due to a one parameter scaling ansatz that transforms the disadvant ages of the basis set superposition error into precious information. T he method is applied to the trimer of hydrogen fluoride and the trimer of water which were both fully geometry optimized up to MP2(FC)/aug-c c-pVQZ level of theory. The electronic interaction energy is predicted to be -15.05 kcal/mol for the trimer of hydrogen fluoride and -15.91 kcal/mol for the trimer of water.