Predicting noncovalent interactions with nonlocal density functional theory

We assess the accuracy of a recently developed nonlocal density functional in treating van der Waals molecular systems. This new functional contains a non-empirical treatment of dispersion interactions and exhibits the appropriate behavior in the high-density limit. We present results for three model noncovalently bonded systems: the methane-benzene complex, a dimethylnitramine dimer, and a dimer of triaminotrinitrobenzene in its crystalline symmetry. Predicted interaction energies are greatly improved with this new approach as compared to conventional density functionals. Intermolecular distances are also improved, though the degree of improvement varies with the character of the intermolecular interactions, with dispersion dominated systems showing the greatest improvement.