A Combined Korringa—Kohn—Rostoker—Discrete-Variational Method for the Electronic Structure of Crystals and Molecules with General Potentials

The recently developed discrete-variational method (DVM) for the energy-band problem has been combined with the Korringa---Kohn---Rostoker (KKR) procedure to adapt the latter to treat general one-electron crystal potentials. Orbitals obtained from a KKR calculation for the muffin-tin average of the full Bloch Hamiltonian are used as trial variational functions for treating the complete problem within the framework of the DVM. Non-muffin-tin corrections originating from all regions of the unit cell are explicitly included by diagonalization of the relevant secular matrix in this basis set. This combination of the DVM and KKR methods to a large extent achieves the main advantages of each scheme and promises to comprise an efficient procedure for calculating the electronic structure of crystal compounds. With this method there is no limitation to a single-type basis set; for some purposes, it may be useful to supplement the KKR orbitals with other trial functions. The high accuracy that is achieved allows definitive conclusions to be drawn concerning the effects of the non-muffin-tin corrections on electronic structure. Illustrative results given for an application of the method to paramagnetic nickel demonstrate this point. An extension of the method is described by which the non-muffin-tin potential and charge-density corrections can be included in the multiple-scattering approach to the electronic structure of molecules.