The effects of homogeneous (temperature-induced) and inhomogeneous (interface-induced) structural disorder on the thermoelastic properties of interface materials are explored by molecular-dynamics simulation. The interface systems considered are superlattices composed of high-angle twist grain boundaries on the (100) plane of a fcc metal at various modulation wavelengths and temperatures. For comparison, the thermoelastic behavior of a perfect fcc crystal is also investigated at the same temperatures. By allowing thermal expansion in some cases, and not in other cases, the explicit effects of the thermal expansion on the elastic properties are explored. We find competing thermal effects of the atomic-level disordering on one hand and the consequent volume expansion on the other. We conclude that atomic-level structural disorder, be it homogeneous or inhomogeneous, can lead to elastic stiffening, provided that the related volume expansions do not dominate the elastic behavior and result in a softening.

• Received 7 October 1991

DOI:https://doi.org/10.1103/PhysRevB.46.2473