title: How to Compute the Fukui Matrix and Function for Systems with (Quasi-)Degenerate States.
abstract: A system in a spatially (quasi-)degenerate ground state responds in a qualitatively different way to a change in the external potential. Consequently, the usual method for computing the Fukui function, namely, taking the difference between the electron densities of the N- and N ± 1 electron systems, cannot be applied directly. It is shown how the Fukui matrix, and thus also the Fukui function, depends on the nature of the perturbation. One thus needs to use degenerate perturbation theory for the given perturbing potential to generate the density matrix whose change with respect to a change in the number of electrons equals the Fukui matrix. Accounting for the degeneracy in the case of nitrous oxide reveals that an average over the degenerate states differs significantly from using the proper density matrix. We further show the differences in Fukui functions depending on whether a Dirac delta perturbation is used or an interaction with a true point charge (leading to the Fukui potential).
authors.affiliation: Ghent University , Department of Inorganic and Physical Chemistry, Krijgslaan 281 (S3), 9000 Gent, Belgium.
authors.forename: Patrick
authors.initials: P
authors.lastname: Bultinck
authors.affiliation: Departamento de Física, Facultad de Ciencias, Universidad de Chile , Casilla 653, Santiago, Chile and Centro para el desarrollo de la Nanociencias y Nanotecnologia, CEDENNA, Av. Ecuador 3493, Santiago, Chile.
authors.forename: Carlos
authors.initials: C
authors.lastname: Cardenas
authors.affiliation: Departamento de Física, Facultad de Ciencias, Universidad de Chile , Casilla 653, Santiago, Chile and Centro para el desarrollo de la Nanociencias y Nanotecnologia, CEDENNA, Av. Ecuador 3493, Santiago, Chile.
authors.forename: Patricio
authors.initials: P
authors.lastname: Fuentealba
authors.affiliation: Dept. of Chemistry and Chemical Biology, McMaster University , Hamilton ON Canada L8S 4M1.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Johnson
authors.affiliation: Dept. of Chemistry and Chemical Biology, McMaster University , Hamilton ON Canada L8S 4M1.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Ayers