The application of a fluctuating charge model for boron nitride networks

A fluctuating charge model (FCM) is developed to consider two-dimensional networks of boron nitride. In the FCM, the charge on each atom site is controlled by parameters linked to the atom's electronegativity and the interactions with other atoms (the coordination environment). The charge held on each atom site is a strong function of the local (first shell) coordination environment. The site charges are shown to be in excellent agreement with those extracted from independent density-functional theory-based calculations. The behavior of the site charges is investigated as a function of the network topology and site disorder. In the first case, specific defects (both site and topological) are introduced, and the spatial "decay" of the local charge to bulk values is assessed. In the second, highly disordered (amorphous) networks are generated, and the distribution of site charges is studied as a function of the degree of topological and site disorder (characterized by the fraction of six-membered rings and mean boron-nitrogen coordination numbers, respectively). Domains of high and low charges are observed to form across a wide range of topological disorder.