The Fermi energy for a three-dimensional, non- relativistic, non-interacting ensemble of identical spin- '"`UNIQ--templatestyles-00000004-QINU`"' 1 ⁄ 2 fermions is given by E F = ℏ ℏ 2 2 m 0 ( 3 π π 2 N V ) 2 / 3 , where N is the number of particles, m 0 the rest mass of each fermion, V the volume of the system, and ℏ ℏ the reduced Planck constant.