New results from semiclassics: chemical accuracy in orbital-free DFT

The successes and failures of approximate density functionals are due to their connection with semiclassical expansions. In the semiclassical limit, relative errors in local density approximations vanish. Carefully derived corrections to that limit have been shown to be far more accurate than our usual DFT approximations. I will discuss important new results in our 20-year-long quest to derive density functional approximations as expansions in hbar. These include both a new correction to the expansion of the exchange energy of atoms and an orbital-free calculation with sub-milli-Hartree accuracy.

[1] Semiclassical Origins of Density Functionals Elliott, Peter, Lee, Donghyung, Cangi, Attila and Kieron Burke, Phys. Rev. Lett. 100, 256406 (2008).

[2] Leading correction to the local density approximation for exchange in large-Z atoms Nathan Argaman, Jeremy Redd, Antonio C. Cancio, and Kieron Burke, Phys. Rev. Lett. 129, 153001 (2022).

[3] Orbital-free functional with sub-milliHartree accuracy, Pavel Okun and Kieron Burke, in preparation.