Abstract: The response function β(r,r′) is a very important quantity in density functional theory(DFT). With the familiar Berkowitz Parr relation: β(r,r′) =- s(r,r′)+f(r)f(r′)S , it can be proved that the negative internal softness kernels equalize to the response function in the atom bond electronegativity equalization model(ABEEM). In this paper, the Fukui function f a—b of a chemical bond a—b and the response function β(a—b,g) and β(a—b,g—h) that is related with a chemical bond a—b are defined based on DFT and ABEEM, and therefore a new method for determining response function is proposed. With this method, the response function and therefore the softness matrix of the closed system are easily obtained. It is shown from many test examples that the response functions obtained in this way can correctly predict the more active site among the various kinds of chemical bonds.

Key words: Atom-bond electronegativity equalization model, Response function, Reactivity