Improved Description of Stereoelectronic Effects in Hydrocarbons Using Semilocal Density Functional Theory.

Serious and systematic errors with popular density functionals occur for isodesmic stabilization energies of n-alkanes, isomerization, and dimerization energies of hydrocarbons and geometries of sterically overcrowded aromatic systems. These functionals are too biased toward the correct description of free atoms. Changing two parameters within the Perdew-Burke-Ernzerhof approximation leads to a new nonempirical functional, PBEsol, that improves the description of large organic systems.