In [B55] we re-examined conditionally converging Ewald's sums using a rigorous mathematical treatment and calculated the Madelung potential well inside a big finite sample of arbitrary shape. It has been found to be given by the Ewald's formula and several additional terms which depend on the shape of the sample and the net dipole moment in the cell.
The theory has been also developed in order to improve the cell-size convergence in ab initio DFT calculations for the general case of arbitrary Bravais lattices [B59].