Finite homogeneous electric fields in the projector augmented wave formalism: Applications to linear and nonlinear response

Computation of the effect of finite homogeneous electric fields in periodic systems is described in the context of the projector augmented wave formalism. Generalizing previous norm-conserving implementations, we compute the polarization using the approach of King-Smith and Vanderbilt [Phys. Rev. B 47 (1993) 1651] fully within the projector augmented wave framework, and then minimizing the electric field enthalpy. Applications to simple systems are provided, including both linear and nonlinear field effects, and photoelastic response.