ABSTRACT
The Quantum Defect Method proceeds from the assumption that when calculating wave functions of electrons in the valence and conduction bands it is a sufficient approximation in many solids to take as a one-electron Hamiltonian an operator which, near any one of the ions in the lattice, is the same as that appropriate to a valence electron in the corresponding free atom. The coupling constant between the solutions depends on a parameter which may be identified with the “extrapolated quantum defect” obtained by drawing a smooth curve through the experimental values of the quantum defect when these are plotted on an energy scale. Kohn and Rostoker have recently proposed a method which is based on a variational procedure derived from an integral equation for the Bloch function. This method assumes that the lattice potential is spherically symmetric about each ion within a sphere inscribed in the atomic cell and is constant in the volume outside the spheres.
