Emergence of film-thickness- and grain-size-dependent elastic properties in nanocrystalline thin films

Molecular dynamics simulations of nanocrystalline Ni revealed that the in-plane Young's modulus of 2.2 nm grained Ni film with similar to 10 grains across its thickness was only 0.64% smaller than that of bulk, while it dropped to 24.1% below bulk value for similar to 1 grain across film. This size dependence arises from the increased number of more compliant grains adjacent to the free surface. Simulations of nanocrystalline diamond revealed that the anharmonicity of the potential curve determined the sensitivity of the Young's modulus to variations in the sample size. (c) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.