Green's-function approach to quantum confinement

We present a rigorous means of computing the electronic properties of a confined system by perturbing the electronic properties of an unconfined, bulk system. Our approach focuses on the Green's function of the confined system. We explain why it is preferable to consider the confined Green's function rather than the confined energy eigenfunctions, and an expression for the change in the Green's function produced by quantum confinement is derived. Finally, we shift our focus to the eigenfunctions and derive approximate results for a spherical nanocrystal with a Green's function methodology. [S0163-1829(98)01515-X].