1 Extension of the B3LYP –Dispersion-Correcting Potential Approach to the Accurate Treatment of both Inter- and Intramolecular Interactions. Gino A. DiLabio1,2 *Mohammad Koleini,1,3and Edmanuel Torres1,41National Institute for Nanotechnology, National Research Council of Canada, 11421 Saskatchewan Drive, Edmonton, Alberta, Canada T6G 2M9;2Department of Physics, University of Alberta, Edmonton Alberta, Canada T6G 2E1;3Department of Chemical and Materials Engineering, University of Alberta, Edmonton Alberta, Canada T6G 2V4;4Faculty of Basic Sciences, Universidad Tecnológica de Bolívar, Cartagena, Colombia. Abstract We recently showed that dispersion-correcting potentials (DCPs), atom-centered Gaussian-type functions developed for use with B3LYP (J. Phys. Chem. Lett. 2012, 3,1738–1744) greatly improved the ability of the underlying functional to predict non-covalent interactions. However, the application of B3LYP-DCP for the β-scission of the cumyloxyl radical led a calculated barrier height that was over-estimated by ca. 8 kcal/mol. We show in the present work that the source of this error arises from the previously developed carbon atom DCPs, which erroneously alters the electron density in the C-C covalent-bonding region. In this work, we present a new C-DCP with a form that was expected to influence the electron density farther from the nucleus. Tests of the new C-DCP, with previously published H-, N- and O-DCPs, with B3LYP-DCP/6-31+G(2d,2p) on the S66, S22B, HSG-A, and HC12 databases of non-covalently interacting dimers showed that it is one of the most accurate methods available for treating intermolecular interactions, giving mean absolute errors (MAEs) of 0.19, 0.27, 0.16, and 0.18 kcal/mol, respectively. Additional testing on the S12L database of complexation systems gave an MAE of 2.6 kcal/mol, showing that the B3LYP-DCP/6-31+G(2d,2p) approach is one of the best-performing and feasible methods for treating large systems dominated by non-covalent interactions. Finally, we showed that C-C making/breaking chemistry is well-predicted using the newly developed DCPs. In addition to predicting a barrier height for the β-scission of the cumyloxyl radical that is within 1.7 kcal/mol of the high-level value, application of B3LYP-DCP/6-31+G(2d,2p) to 10 databases that include reaction barrier heights and energies, isomerization energies and relative conformation energies gives performance that is amongst the best of all available dispersion-corrected density-functional theory approaches. *Author of correspondence. Phone: +1-780-782-6672, E-mail: [email protected]
2 IntroductionThe ability to model structures and properties of systems in which non-covalent interactions are important is critical in a number of areas of chemistry, physics and biology, as is illustrated by the complexities of protein structure.