Lattice distortion and its effects on physical properties of nanostructured materials

A theoretical model is developed to understand the basic mechanism of the deviation of a crystal lattice from the perfect structure in nanostructured materials. The interface tension and the stress field induced by the excess volume in the grain boundaries are the two main reasons for lattice distortion. Based on this model, the contribution of the lattice distortion to the thermal expansion coefficient of nanostructured materials is analysed quantitatively. The results show that the unusual physical properties of nanostructured materials result not only from grain boundaries, but also from nanocrystallites.