We present the One-orbital Ensemble Self-Consistent Field (OE-SCF) method, an alternative DFT solver based on orbital-free DFT that extends the applicability of DFT to system sizes beyond the nanoscale while retaining the accuracy required to be predictive. OE-SCF samples ensemble N-representable densities while still searching for a single one-particle Hamiltonian eigenstate, avoiding costly diagonalizations. We implemented this method in recently developed OF-DFT software DFTpy, which is written entirely in python. Employing merely a single CPU, we carried out the largest ab initio simulation for silicon-based materials to date. OE-SCF is able to converge the energy of bulk-cut Si nanoparticles as a function of their diameter up to 16 nm, for the first time reproducing known empirical results. We model polarization and interface charge transfer when a Si slab is sandwiched between two metal slabs where lattice matching mandates a very large slab size. We have provided important preliminary results indicating that the proposed OE-SCF method will replace direct energy minimization as the solver of choice in orbital-free DFT software due to its superior stability and computational time to solution. Simultaneously, because OE-SCF only needs to evaluate complex functionals only a dozen times and insensitive to the system size, it will enable formulation and deployment of even more complex density functionals than currently available for use in predictive beyond-nanoscale DFT simulations.

An efficient DFT solver for nanoscale simulations and beyond

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.