Partitioning the DFT exchange-correlation energy in line with the interacting quantum atoms approach

Abstract

The interacting quantum atoms (IQA) energy partition has given important insights about different systems and processes in theoretical chemistry. Given its intrinsic dependence on first- and second-order density matrices, IQA is only cleanly defined within wavefunction methods. This means that, despite the importance of density functional theory (DFT) in electronic structure methods, a neat IQA–DFT implementation is not straightforward. This work addresses this issue through a new implementation of IQA within the Kohn–Sham formalism of DFT in conjunction with hybrid and non-hybrid functionals that contributes further to that already presented (Maxwell et al. in Phys Chem Chem Phys, 2016. doi:10.1039/C5CP07021J). For this purpose, we use additive exchange-correlation (xc) energies, defined within the IQA approach, to scale the one- and two-atom terms of the Kohn–Sham xc energy. This leads to an exact partition of the xc DFT energy of a molecule into intra-atomic and inter-atomic contributions. The suggested method is illustrated with several molecules together with some of the most popular local and hybrid DFT functionals. Overall, we anticipate that the approach put forward in this work will prove useful in getting further insights of phenomena in chemistry which are properly described with DFT .