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

It is demonstrated that the topological arrangement of atoms can guarantee 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 applications are presented in tight-binding approximation. It was found that graph theory can be used even if the atoms have more than one atomic orbital. Also, the localization properties of the topologically determined eigenvalues are studied. (C) 1993 John Wiley & Sons, Inc.