On the use of fractional charges for computing Fukui functions

Condensed Fukui indices have been computed for a series of organic molecules using fractional charges, as opposed to the conventional approach of performing calculations with the molecular cation and anion. Besides the Fukui function, the eigenvalues, μ, of the highest occupied molecular orbital and lowest unoccupied molecular orbital are also obtained from finite differences. Using a full electron produces errors of up to several hundred percent in the value of μ, and errors of about 5% in atomic Fukui indices. Using a fractional charge of 0.1 can reduce these computational errors significantly.