Excitation Spectra of Disordered Systems. I. General Theory

Abstract
The approximate method developed by Wu for the study of the lattice dynamics of one‐dimensional disordered systems is extended to be applicable to two‐ and three‐dimensional systems. The basic ideas of the approach are reviewed and the multi‐dimensional form of the approximation is developed. Applications are made to periodic lattices in all dimensions and the one‐dimensional disordered lattice. Comparisons with previous results show excellent agreement.