Performance of optimized atom-centered potentials for weakly bonded systems using density functional theory

Recently, we have introduced a scheme for optimizing atom-based nonlocal external potentials within the framework of density functional theory (DFT) in order to systematically improve the description of molecular properties [Phys. Rev. Lett. 93, 153004 (2004); J. Chem. Phys. 122, 014113 (2005)]. In this study, we investigate a small library of dispersion-corrected atom-centered potentials (DCACP's) for C, Ar, Kr, and Br. To this end, we calibrate DCACP's in order to reproduce the equilibrium distance and binding energy of MP2 potential energy surfaces of the weakly bonded homodimers Ar-2, Kr-2, and (Br-2)(2), In all cases studied, using DFT with the generalized gradient approximation functional BLYP and the DCACP's, the influence of dispersion forces on equilibrium and transition-state geometries, interaction energies, and transition barriers can be reproduced in good agreement with MP2 calculations and without any significant increase in computational cost. The transferability of the DCACP's to other systems is assessed by addressing various weakly bonded complexes. We investigate (i) ideal van der Waals clusters of the type ArnKrm (for all n,m={0, 1, 2, 3, 4} and 2 <= n+m <= 4), (ii) the effect of DCACP's on covalent bonds and conformers of the hydrocarbon molecule cyclooctatetraene which features a system of pi bonds, and (iii) the competition of simultaneous electrostatic and dispersion forces for the equilibrium structure and transition states of the hydrogen bromide dimer (HBr)(2). In all cases, the performance of the DCACP's to these extended set of systems is remarkably good.