Optimally smooth norm-conserving pseudopotentials

Modern norm-conserving pseudopotentials are constructed to satisfy a set of criteria for the matching of pseudo- and all-electron eigenvalues and wave functions. In practice, it is also desirable that they be as smooth as possible, so that their reciprocal-space representation decays as quickly as possible. To this end, a simple modification of a standard pseudopotential generation scheme is developed. The new, smoother potentials are shown to decay significantly faster in reciprocal space, with no loss of transferability.