Energy Band Calculations by the Augmented Plane Wave Method

Abstract

This chapter describes some of the energy band calculations that have been made at M.I.T. To carry out the calculation in a practical fashion, one derives a secular equation connecting the various plane waves, each supplemented by its spherical part inside the spheres; it is now customary to refer to such a function as an augmented plane wave (APW). A few of these have been published, but a number of them are still in a preliminary stage, and the description given in the chapter is not intended to do more than indicate in a general way the type of result found. The chapter provides the calculation on iron carried out by Wood and shows the energy bands. The characteristic is of course the bands of 3d character interposed in the middle of the 4s-like band. Wood's calculations are made for a nonmagnetic potential; that is, the same potential is used for electrons of both spin. However, Wood has also estimated the effect of using different potentials for the two spins, to give an energy band description of ferromagnetism.