Transferable local pseudopotentials derived via inversion of the Kohn-Sham equations in a bulk environment
The lack of accurate transferable local pseudopotentials represents one of the remaining barriers to the general application of orbital-free density functional theory (OF-DFT, a linear scaling technique). Here we report a method to generate high quality ab initio local pseudopotentials (LPS’s) for use in condensed matter DFT calculations. We exploit the first Hohenberg-Kohn theorem, which states that the external potential is one-to-one mapped to the ground-state electron density. By employing a scheme for inverting the Kohn-Sham (KS) equations due to Wang and Parr, we iteratively solve for the KS effective potential vKSeff(r) until it reproduces a target density. From vKSeff(r) we derive a global LPS for the entire system. This global LPS is then further decomposed to obtain an atom-centered LPS. We show that LPS’s derived from bulk environments are substantially more transferable than those derived from atoms alone. In KS-DFT tests on Si, we show that this bulk-derived LPS can reproduce accurately phase orderings predicted by nonlocal pseudopotentials for both metallic and semiconducting phases. We then tested this LPS in OF-DFT calculations on Si crystals, where we demonstrate that this bulk-derived LPS (BLPS), combined with a linear-response-based kinetic energy density functional with a density-dependent kernel, correctly predicts a diamond structure ground state for Si in an OF-DFT calculation. Other bulk properties, such as defect formation energies and transition pressures are also presented as tests of this BLPS. This approach for deriving LPS’s isolates much of the remaining error in OF-DFT to the kinetic energy density functional, providing means to test new functionals as they become available.