ON THE ELECTROSTATIC THEORY FOR QUADRUPOLAR MATERIALS

It is shown that to describe properly the electrostatic theory of quad rupolar materials, the electrostatic energy density of the medium has to contain a term quadratic in the spatial derivatives of the electros tatic field. In this manner well known results are recovered. Furtherm ore it is shown that due to the quadrupolar properties of the medium, an abrupt variation of the electric potential near the electrode is ex pected. This surface variation takes place over an intrinsic semi-micr oscopic length defined by the ratio between the phenomenological coeff icient connected with the new electrostatic energy term, and the usual dielectric constant. However, the surface variation of the electric p otential is independent of this new coefficient, but it depends only o n the electric quadrupolar density and on the dielectric constant. Thi s new result is also obtained in the frame of the usual theory.