ABSTRACT

V(r) = /„ (z ) elk^ e ,k>yu j r ) = f ,( r )« „ ( r ) . ( 1) A clear perspective on the formulation of the band structure arises on using the principle of least action in setting up the k»P model.[l] A number of issues such as derivative

operator-ordering are resolved in a very natural manner, leading to a number of insights into the approximations that are invoked in the modeling. The action integral that leads to the Schrodinger equation for the valence bands is given by

The directed derivatives d and d act on the functions appearing to the left and to the right, respectively. All the bands are treated within degenerate perturbation theory. In the following, the integral over time is irrelevant since we are concerned with the time independent band structure problem.