Variational projector augmented-wave method

In Kohn–Sham electronic structure computations, wave functions have singularities at nuclear positions. Because of these singularities, plane wave expansions give a poor approximation of the eigenfunctions. The PAW (projector augmented-wave) method circumvents this issue by replacing the original eigenvalue problem by a new one with the same eigenvalues, but smoother eigenvectors. Here a slightly different method, called VPAW (variational PAW), is proposed and analyzed. This new method allows for a better convergence with respect to the number of plane waves. Some numerical results on an idealized case corroborate this efficiency.