Abstract. Let V be a periodic potential on R 3 that is smooth everywhere except at a discrete set S of points, where it has singularities of the form Z/ρ 2 , with ρ(x) = |x − p| for x close to p and Z is continuous, Z(p) > −1/4 for p ∈ S. We also assume that ρ and Z are smooth outside S and Z is smooth in polar coordinates around each singular point. Let us denote by Λ the periodicity lattice and set T := R 3 /Λ. In the first paper of this series [20], we obtained regularity results in weighted Sobolev space for the eigenfunctions of the Schrödinger-type operator H = −∆ + V acting on L 2 (T), as well as for the induced k-Hamiltonians H k obtained by resticting the action of H to Bloch waves. In this paper we present two related applications: one to the Finite Element approximation of the solution of (L + H k )v = f and one to the numerical approximation of the eigenvalues, λ, and eigenfunctions, u, of H k . We give optimal, higher order convergence results for approximation spaces defined piecewise polynomials. Our numerical tests are in good agreement with the theoretical results.