Recent Advances in Software for a Density Functional Theory of Molecular Fragments

 Partition Density Functional Theory (P-DFT) is a quantum chemistry method in which the system is fragmented into non-interacting components, and the energy is given by functionals of the fragment densities. The method is unique in the sense that it corrects for density functional approximation errors and sheds light on the individual structure of fragments within a molecule. In this work, we discuss the fundamental aspects of the theory as well as its challenges, and we introduce two software packages that were written to advance the understanding and applicability of the theory. The first, n2v focuses on the numerical procedure to obtain a potential that generates a given density, and the second, pyCADMium performs very accurate P-DFT calculations in diatomic molecules. Both packages are fully open-source and thus can be used and repurposed with any intention. We hope that these advances can be used to develop everyday embedding calculations.