PNNL

Abstract

We present a new interaction potential for hydrogen bonds and used it to derive an analytic relationship between the hydrogen bond strength and the underlying change in the covalent bond that participates in the hydrogen bond. The model includes components describing the covalent D-H bond of the hydrogen bond donor via a Morse potential, the Pauli repulsion, and electrostatic interactions between the constituent fragments using a linear expansion of their dipole moment and a quadratic expansion of their polarizability tensor. We fitted the parameters of the model using ab-initio electronic structure results for six hydrogen bonded dimers namely NH3-NH3, H2O-H2O, HF-HF, H2O-NH3, HF-H2O, and HF-NH3 and validated its performance for extended parts of their potential energy surfaces resulting in a Mean absolute error (MAE) ranging from 0.07 to 0.31 kcal/moThe model describes the Energy - Structure relationship in terms of a single structural parameter, namely the elongation of the donor’s covalent bond (?rHB), and suggests the novel relationship of 8.0 kcal/mol pm-1 (or 0.8 kcal/mol per 0.001 °A elongation). This structural parameter is easily obtained from theory and can serve as the single descriptor of the strength of individual hydrogen bonds