材料期刊网

The vibrational densities of states for the diffusion-limited aggregate with varying elastic force consstants are calculated by the recursion method of Haydock, Heine and Kelly. It is found that the spectrum with central forces is very different from that with isotropic forces which is characterized by a power-law behaviour in the fraction frequency regime. An interesting crossover is also observed when the ratio of the central to the non-central force constants of the Born model varies from alpha/beta = 1 to alpha/beta = inifity.