Excitations in amorphous pyramidally bonded solids. II. Phonons

Phonon state densities are calculated for crystalline and amorphous As. The results indicate a strong analogy between the electronic $p$ states and the vibrational states. This isomorphism is used to derive relationships between the electronic and phonon coupling constants. The effects of topology upon the vibrational excitations in pyramidal solids are studied. A new model for infrared absorption is presented. The resulting spectra agree well with experimental measurements. Finally, inelastic neutron-structure factors are calculated and are used to interpret recent experimental results.