The authors describe a method for performing density-functional calculations for topologically disordered condensed matter. This method combines the recursion, and the linear-muffin-tin-orbital (LMTO) methods, and uses the tight-binding representation. In the present version, the LMTO matrix elements are evaluated in the atomic-sphere approximation (ASA). Various levels of approximation for the ASA Hamiltonian, such as the two-center tight-binding one, are systematically derived and tested. The method is applied to crystalline BCC Fe and to amorphous Fe80B20. Charge self-consistency is only treated for the average Fe and the average B atoms. The Fe-B bonding is found to be covalent. A Stoner theory is derived and used to describe the ferromagnetism. The structures of their density of states for ferromagnetic Fe80B20 agree in detail with reliable photoemission data.
 

Physical Review B, 44 3577-98, 1991.