Placement of the fictitious boundary in the charge iteration procedure for unbounded electrical field problems

The charge iteration procedure, recently presented by the authors for the FEM solution of unbounded electrical fields, makes use of a fictitious boundary whose position strongly affects convergence properties and performance in terms of computational effort. In this paper the problem of the optimal placement of this boundary is first addressed analytically in the case of simple systems and then it is illustrated how the obtained conditions can be used for more complex systems so as to offer simple criteria for the application of the procedure to practical cases