Chapter 3 Density functional theory of the ground-state magnetic properties of rare earths and actinides

Abstract

This chapter discusses the density functional (DF) theory of the ground-state magnetic properties of rare earths and actinides. The results of calculations made using DF theory are used, this is the theory used for nearly all electronic structure calculations in solids. DF theory is a ground-state theory—a variational principle for the ground-state energy in terms of the electron density, or electron spin density. The eigenvalues that are obtained in this theory are the functional derivatives of the total energy with respect to the density or spin density. They are not in general simply related to measured quantities, although the temptation to compare the two is rarely resisted. DF theory contains an unknown functional for the exchange and correlation energy into which most of the lack of knowledge of the contribution of many-body interactions to the total energy is placed. The functional is replaced by an approximate one, which is derived for a homogeneous electron gas with constant density. The functional and its functional derivatives are used to obtain the potential in terms of the density; the constant density is then replaced by the real density the local density or spin density approximation (LDA or LSDA).