Extrapolation functions for calculating stretching frequencies of local OH bonds of water molecules

摘要

Complete basis set (CBS) limit extrapolation of ab initio electronic energies of a water dimer has been performed over a range of OH bond distances. The inverse power, exponential, and stretched exponential functions used as an extrapolation function give different extrapolated electronic energies. Using the extrapolated energies, we calculated the fundamental and the first overtone transition frequencies of the OH bonds of the hydrogen-bond (HB) donor in the dimer. The three extrapolation functions give almost the same stretching frequencies, which are in reasonably good agreement with the experimental frequencies, but the exponential form gives slightly better agreement.