Infinite, periodic systems in external fields -- an efficient, theoretical method

The response of periodic systems to external electric fields is a challenging theoretical problem. We show how the vector potential approach yields a numerically efficient treatment of the combined electronic and nuclear response to a finite static field. Our method is based on a self-consistent reformulation of the charge flow term in the single particle Hamiltonian. Careful numerical implementation yields a treatment whose computational needs are only marginally larger than those of a conventional field-free calculation. To prove the method we have performed model calculations for a qusi-one-dimensional (polymeric) system. The model contains all essential elements of an ab initio Kohn-Sham or Hartree-Fock Hamiltonian but allows for extensive testing.