Recovering orbital information from orbital-free density functional theory

Linear-scaling orbital-free density functional theory (OF-DFT) is capable of calculating properties of large systems of thousands of atoms at quantum mechanical level. The major obstacles of OF-DFT lie in the computation of the kinetic energy and the nuclear-electron interaction energy. The latest linear-response based kinetic energy density functional can treat metallic materials in OF-DFT almost as accurate as Kohn-Sham (KS) DFT; however, the present best OF-DFT results for covalent materials still possess large unacceptable errors. We have developed a new linear-scaling method, called orbital-corrected OF-DFT (OO-DFT), to improve OF-DFT by solving the KS equations under a fixed KS effective potential, which is constructed from the electron density obtained from OF-DFT calculations. For covalent materials, OO-DFT corrects errors in OF-DFT with only one iteration of solving the KS equations. Our work paves the way for the general applications of OF-DFT on large systems.