Anisotropic repulsion potentials for cyanuric chloride (C3N3Cl3) and theirapplication to modeling the crystal structures of azaaromatic chlorides

A series of nonempirical intermolecular potentials has been developed for t he cyanuric chloride dimer, using the overlap model to determine the anisot ropy of the repulsive wall around each atom. Calibration against intermolec ular perturbation theory calculations enables the penetration and charge-tr ansfer energy to be explicitly included with the exchange-repulsion to give a simple repulsion model in an anisotropic atom-atom form. These model rep ulsion potentials are used in conjunction with an atomic multipole electros tatic model and an atom-atom dispersion model to give nonempirical potentia l models, which are tested for their ability to reproduce the crystal struc ture of cyanuric chloride. The best nonempirical potential is successfully used to construct a simpler transferable model for closely related azaaroma tic chlorides. The nonempirical potential reproduces the experimental space group of cyanuric chloride, unlike some empirically fitted repulsion-dispe rsion potentials. This first nonempirical repulsion potential to model the polar flattening of Cl atoms also reproduces the N . . . Cl and Cl . . . Cl interactions in other crystal structures.