Consider a "crystal" consisting of two nuclei and two electrons.
(a) Taking into account all the pairs of interactions, find the potential energy 1 of the system as a function of d.
(b) Assuming the electrons to be restricted to a one-dimensional box of length 3d, find the minimum kinetic energy of the two electrons.
(c) Find the value of d for which the total energy is a minimum.
(d) Compare this value of d with the spacing of atoms in lithium, which has a density of 0.53 g/cm3 and an atomic weight of 7.