The effect of surface stress on nano-structures
Lawrence Livermore National Laboratory, US
surface stress, surface elasticity
Novel experimental tools as well as ab-initio calculations can probe properties and behavior of materials with characteristic dimensions down to a few nanometers. While results from these investigations reveal and quantify size effects, their interpretation has been problematic in terms of continuum mechanics and thermodynamics. A valid and rigorous theoretical formulation of surface mechanics and surface thermodynamics is highly desirable to allow a seamless description of size effects from the atomic level to the meso- and macro-scales. We introduce the theory of Gurtin and Murdoch and apply it to the recent experimental and computational results on nano-particles, thin films, and nanowires. We demonstrate that this theory provides relationships for size effects on the elastic behavior of nanostructures that agree with experimental results as well as atomistic predictions from ab initio and EAM calculations. Applying this theory to nano-meter sized voids and helium bubbles in solids, we demonstrate the different roles played by the chemical surface tension and by the surface stress on the thermodynamic stability of bubbles and on their effect on the yield strength.
Nanotech 2008 Conference Program Abstract