A pinboard by
Ganesh Iyer

A two-scale methodology is developed for simulation of surface stress and its effects are studied

Three illustrative surfaces are considered ({100}, (110} and {111}) and aluminium is used as model material. This is because Al has a high stacking fault energy making it difficult for the dislocations to split into partials. High symmetry surfaces like the {100} and (111} are in a state of equi-biaxial stress. The utility of the model developed is highlighted by demonstrating the effect of surface stress on the: (i) residual stress distribution in a thin slab & (ii) lattice parameter change of nanoscale free-standing crystals (of spherical, octahedral and cubical geometries). The model is validated by comparison with theoretical, experimental and computational results available in literature. The approach developed for the simulation of surface stress is applied to the computation of lattice parameter of hollow metal nanoshells (MNS). In the case of MNS there are two surfaces, the surface stress on the outer surface tends to contract the radial lattice parameter, while the inner surface stress has the opposite tendency. Two interesting observations arise from the computational analysis: (i) a lattice expansion (in the radial direction) purely due to surface stress effects in a metallic system (thin walled) and (ii) an anomalous lattice expansion in the case of very thin walled MNS. The term anomalous has been used as for the case of very thin walled MNS, the outer surface stress leads to an expansion of the radial lattice parameter and this is a Poisson effect driven phenomenon.