Analysis of Atomic Contributions to the Energy in Water Clusters: from a Dimer to a Decamer

Abstract

Sixteen water clusters with the number of molecules from 1 to 10 are calculated by quantum chemical methods (PBE1PBE0/def2-TZVPP). Changes in atomic energies (by IQA) due to the formation of hydrogen bonds (H-bonds) are analyzed in the dimer, trimer, tetramer, pentamer, hexamer (planar and twist-conformations), heptamer, octamer, and decamer. Energy gains are shown to differ substantially for the donor and acceptor molecules, with destabilization of the “free” hydrogen atom decreasing with increasing cluster, while for the hydrogen atom involved in the H-bond it can be replaced by stabilization. Correlation (R² = 0.9938) is found between the exchange-correlation energy (IQA) and the H-bond energy, which is estimated by the potential energy density at the (3, –1) bond critical point according to the Espinosa approach.