Optimization of the calculation of a local electric field in crystals by the transient-region method

The specific features of using the method of transient-region for calculating local electric fields and the corresponding potentials are considered on examples of the calculations for NaF, CsCl, and LiNbO₃ crystals. It is shown that for crystals with a primitive cubic lattice, this method can provide any given accuracy of the calculated Madelung constant; for displacive-type ferroelectrics (LiNbO₃), the method allows the calculation of the local electric field with a very high accuracy. It is emphasized that for each specific object, one has to carefully select the parameters of the convergence function.