  We propose a linear-combination-of-pseudo-atomic-orbitals scheme for a finite
electric field method based on the modern theory of polarization. We derive the
matrix elements of the effective potential for the field and the corresponding
terms of the forces on atoms. In addition, we successfully evaluated the
dielectric constants and Born effective charges of typical semiconducting and
insulating materials. Our formalism will aid in the study of materials under
electric fields.
