SPECIFIC-HEAT OF NANOSTRUCTURED MATERIALS

We study the thermal properties of nanostructured materials assuming t hat a sizable fraction of atoms in the intercrystalline boundary regio n move in local bistable soft potentials. The extra degrees of freedom are represented by a set of two-level systems. The effects of disorde r are described by local Gaussian random energies representing the asy mmetry of the soft potentials, and by random finite-range pairwise int eractions. Using the pseudospin formalism and the replica method known from the theory of dipolar glasses, the internal energy and the exces s specific heat are evaluated. It is shown that in the replica symmetr ic case, corresponding to a mean field approximation, the excess speci fic heat is linear at low temperatures and goes through a broad maximu m at higher temperatures.