Approximations in the computation of molecular polarization maps

SUMMARY In order to assess the effect of different approximations involved in the computation of molecular polarization potential maps, two sources of inaccuracies were analysed in the present work. First, the effect of non-linear contributions of the electric field, and second the effect of using an uncoupled Hartree‐Fock perturbation scheme for its evaluation. The study was carried out at the Hartree‐Fock level using the standard basis sets: 3‐21G, 6‐31G and 6‐31G* on six different molecules: hydrogen cyanide, formaldehyde, urea, acetone, furan and pyrrole. The results show that non-linear effects can be up to 4% of the total polarization when a unit charge is used for the computation of the polarization maps. Regarding the use of an approximate treatment for the calculation of the perturbation energy, the study reflects that the average underestimation of the polarization potential provided by the uncoupled scheme ranges from 4 to 15% depending on the system considered.