Improving B3LYP Heats of Formation with Three-Dimensional Molecular Descriptors

In the present work, we propose the X-3D method that extends the B3LYP method by correcting its errors on heats of formation of hydrocarbons (HCs) with three-dimensional (3D) molecular descriptors. Inspired by the widely used Wiener index, these 3D descriptors are developed to improve over the original B3LYP method for a better description of atom-atom, atom-bond and bond-bond interactions. On top of a training set of only 45 species, the X-3D method is validated against various sets of different chemistry, displaying an overall near chemical accuracy. In particular, X-3D improves over B3LYP, reducing its mean absolute errors from 28.4 to 0.3 kcal/mol for (Set 1) 21 n-alkanes up to n-C32H66, from 19.3 to 0.6 kcal/mol for (Set 2) n-C7H16 and its branched isomers, from 29.5 to 1.6 kcal/mol for (Set 3) 36 polycyclic saturated HCs, from 8.6 to 1.1 kcal/mol for (Set 4) 41 C6H8 isomers of rings, alkenes, alkynes, and cumulenes, from 20.3 to 0.6 kcal/mol for (Set 5) 41 benzene-based compounds, and 8.1 to 1.3 kcal/mol for (Set 6) 66 radicals, etc. Comparisons with the G4 results are also presented. (C) 2016 Wiley Periodicals, Inc.