Using benchmark quality CCSD(T)-F12b data, a simple statistical model for halogen bond equilibrium interaction energies has been developed. Only a single parameter per molecule (X and B) is required, resulting in the simple form: E = XB / Rn, where R is the equilibrium separation between the two molecules engaged in a halogen bond. When n = 4, the RMSE over a validation set is just 0.28 kcal/mol, providing better results than popular DFT functionals for non-covalent interactions.
A Jupyter notebook has been prepared that includes a simplified walkthrough of the fitting and analysis of the model, along with an example of how parameters for new molecules can be found.
A simple model for halogen bond interaction energies. R.A. Shaw and J.G. Hill, Inorganics, 2019, 7, 19 (open access).