Study of a Smooth Interpolation Between Hirshfeld and Iterative Hirshfeld Population Analyses

A smooth interpolation between the Hirshfeld and the iterative Hirshfeld isolated atomic densities used to determine the weight function that distributes the mo-lecular electronic density among the atoms is proposed to analyze the effect of the Fukui function on the atomic charges obtained. The interpolation makes use of a parameter alpha, that leads to the Hirshfeld weight function when alpha = 0, and to the iterative Hirshfeld weight function when alpha = 1. Through the calculation of the correlation coefficient R2 between these charges and those corresponding to fits of the electrostatic potential, it is found that R2 presents a maximum when alpha is equal to 0.95, and is almost constant for values of alpha between 0.85 and 1.0. The second main correlation was found with the atomic dipole moment corrected Hirshfeld charges that leads to a maximum when alpha lies between 0.5 and 0.6. Thus, the additional parameter that results from the interpolation may be used to obtain charges similar to those found through schemes that only assign charges, to obtain at the same time the atomic densities that add up to the molecular electron density, or the additional parameter may be used to find a set of charges in a molecule aimed to give a better description of a specific property, delivering at the same time a set of atomic densities that may be very important to derive other properties of the atoms in a molecule.