All-electron plane-wave electronic structure calculations

We demonstrate the use of the plane wave basis for all-electron electronic structure calculations. The approach relies on the definition of an analytic, norm-conserving, regularized Coulomb potential, and a scalable implementation of the plane wave method capable of handling large energy cutoffs (up to 80kRy in the examples shown). The method is applied to the computation of electronic properties of isolated atoms as well as diamond, silicon, MgO, solid argon, and a configuration of 64 water molecules extracted from a first-principles molecular dynamics simulation. The computed energies, band gaps, ionic forces and stress tensors provide reference results for the validation of pseudopotentials and/or localized basis sets. A calculation of the all-electron band structure of diamond and silicon using the SCAN meta-GGA density functional allows for a validation of calculations based on pseudopotentials derived using the PBE exchange-correlation functional. In the case of (H₂O)₆₄, the computed ionic forces provide a reference from which the errors incurred in pseudopotentials calculations and in localized gaussian basis sets calculations can be estimated. All calculations are performed using the Qbox code (http://qboxcode.org).