On non-negativity of Fukui function indices. II

In this article we have tried to critically analyze the factors which cause the condensed Fukui function (FF) indices [f(r)] to attain a negative valu e in some cases. The evaluation of condensed FF indices needs finite-differ ence approximation to the electronic charge densities, and the finite-diffe rence approximation needs partitioning of the electronic charge to the cons tituent atoms. In a previous article [J. Chem. Phys. 110, 8236 (1999)] we h ave argued that the probable factors, which cause the FF indices to appear negative in some cases, may be (i) the improper charge partitioning techniq ues adopted to evaluate f(r); (ii) large change in the electron number (Del ta N = 1) when f(r) is evaluated in condensed form using the finite-differe nce approximation. In this article we want to focus more on the first facto r. The present study shows through pictorial as well as numerical demonstra tions of the charge-density difference [rho(neutral)((r) over bar)-rho(cati on)((r) over bar) and rho(anion)((r) over bar)-rho(neutral)((r) over bar)] plots, how the negative condensed FF value appears with the use of improper charge partitioning and how the use of Hirshfeld partitioning can solve th is problem. (C) 2000 American Institute of Physics. [S0021-9606(00)30128-3] .