NUMERICAL EVALUATION OF THE INTERNAL ORBITALLY RESOLVED CHEMICAL HARDNESS TENSOR - 2ND-ORDER CHEMICAL-REACTIVITY THROUGH THERMAL DENSITY-FUNCTIONAL THEORY

In a previous work we have presented a numerical procedure for the cal culation of the internal chemical hardness tensor at the molecular orb ital resolution level from standard density functional calculations. I n this article we describe an improvement of our method using the ther mal extensions of density functional theory. Furthermore, new concepts are introduced in the orbitally resolved theory of chemical reactivit y. Traditional molecular orbital theories of chemical reactivity are b ased only on considerations concerning the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUIMOs) of molecules, supposed to describe the behavior towards electrophiles , respectively, nucleophiles. By applying our methodology to two test molecular systems, namely water and ferrocene, we show how chemical re activity can be differentiated against hard and soft electrophiles (ac ids) and hard and soft nucleophiles (bases). As a by-product of the nu merical algorithms being used, a self-consistent method for calculatin g the molecular chemical potential is also described. (C) 1998 America n Institute of Physics. [S0021-9606(98)01721-8]