The Fermi energy of ellipsoidal nanoparticles.

We introduce a simple analytical model in order to find the energy spectrum of ellipsoidal samples. For this purpose, the perturbation theory is applied. The eigenvalues of the energy are of the size and shape dependent form, which leads to the dependence of the samples properties. In particular, the Fermi energy is discussed in the context of the deformation of single nanoparticle from spherical shape and their ensemble.