Hartree-Fock energy levels in solids: Application to argon

Abstract
We examine the reliability of first-principles electronic calculations performed with the orthogonalized-plane-wave method and the Gaussian representation of occupied orbitals. A good feature of such a procedure is that the exchange potential in its nonlocal form can be included rigorously and the matrix elements are still in analytic form. As a specific application, we consider the case of argon, and we compare our results with previous calculations.