CAPACITIVE NATURE OF ATOMIC-SIZED STRUCTURES

The capacitance of an N-electron system is established by deriving the atomistic connection between the capacitive energy, the ionization po tential, and the electron affinity of the charged system; it is shown further that this connection leads to the linkage of the capacitive en ergy to the difference between the lowest unoccupied and the highest o ccupied Kohn-Sham orbital energies of the system. An illustrative exam ple is used to show explicitly the microscopic behavior of the derived capacitance for a finite electron system, and to discuss the tendency of the derived capacitance to limit toward the classical electrostati c capacitance as the system becomes macroscopically large. Discussions relevant to atomic and molecular systems are included.