VB-DFT: a nonempirical hybrid method combining valence bond theory and density functional energies

A nonempirical procedure is presented for combining the valence bond (VB) methodology with density functional theory (DFT). The method, called VB-DFT, is based on partitioning the system into two coupled electronic subsets, one treated by DFT and the other by VB theory. The DFT energy component includes the exchange correlation potential while the coupling involves electron repulsion and exchange interactions. Tests and applications show that the VB-DFT hybrid method has the qualities of a VB method along with a quantitative advantage over VB-only methods with traditional core–valence separation.