Inelastic neutron scattering in the amorphous and the crystalline state: The phonon-fracton density of states

Abstract

Inelastic neutron scattering has been used to obtain the density of states, G(E), for both crystalline and amorphous samples of diglycidyl ether of bisphenol A, the monomer basis of most epoxy resins. For the crystalline material G(E) is proportional to ${\mathrm{E}}^2$ at low E while in the amorphous state the results confirm our earlier work in which G(E) while initially proportional to ${\mathrm{E}}^2$, varies as a higher power of E above 1.2 meV. Calculations of the specific heat, C, show that both the amorphous and crystalline samples have a peak in C/${\mathrm{T}}^3$ in the liquid-helium range. Hence the use of C to explain the differences between crystalline and amorphous materials can be misleading.