STABLE ELECTRONIC-ENERGY LEVELS IN THE PRESENCE OF OFF-DIAGONAL DISORDER

It is demonstrated that the topological arrangement of atoms can guara ntee the existence of stable electronic eigenvalues. These levels are stable in the presence of off-diagonal disorder. Graph theory is used to describe the topological structure of the Hamiltonian. The actual a pplications are presented in tight-binding approximation. It was found that graph theory can be used even if the atoms have more than one at omic orbital. Also, the localization properties of the topologically d etermined eigenvalues are studied. (C) 1993 John Wiley & Sons, Inc.