  The electron interaction energy of two interacting electrons in a circular
quantum dot (with hard wall confinement) is investigated in the framework of
the semi-classical Wentzel-Kramers-Brillouin (WKB) approximation. The two
electrons are assumed to be in an infinitely deep well of radius $r_0$, in a
simple configuration with one electron fixed at the origin. The corresponding
Schrodinger equation, with hard wall boundary conditions, is also solved
exactly by numerical integration. It is observed that the agreement between the
two energy values is quite good, suggesting that the WKB approximation works
well for such a confined quantum system as well. This may provide motivation to
extend this to more realistic confined potentials.
