Reconstructing All-Electron Densities and Static Structure Factors from General Pseudopotentials

Electron densities provide valuable information, such as atomic charges and static structure factors, but all-electron densities can be computationally expensive to obtain. This work presents a method to approximate all-electron densities from pseudopotential electronic structure calculations, called the Valence Electrons Plus Independent Cores (VEPIC) model. For each pseudopotential in the calculation, a pseudocore is defined, and this is added to the ab initio pseudovalence density. Electron densities obtained this way yield accurate static structure factors, as well as atomic charges and dipoles from the Hirshfeld and Minimal Basis Iterative Stockholder methods, compared with those from all-electron calculations. While the total density of this model matches the all-electron density in the valence region, the model lacks core polarization, which is present in the Projector Augmented Wave (PAW) method, making the VEPIC model an intermediate between the Independent Atom Model (IAM) and the PAW model in terms of accuracy. It is also intermediate between the two in terms of computational complexity, as it only requires the pseudovalence density, unlike PAW, which additionally requires processing every pseudovalence wave function in the system.