Nanoplate elasticity under surface reconstruction

摘要

Using classical molecular statics simulations, we show that nanoplate elasticity strongly depends on surface reconstruction and alignment of bond chains. Because of its well-established surface reconstructions and the readily available interatomic potential, diamond-cubic silicon is the prototype of this study. We focus on silicon nanoplates of high-symmetry surfaces, {111} and {100}; with 7 X 7 and 2 X 1 reconstructions. Nanoplates with unreconstructed {111} surfaces are elastically stiffer than bulk. In contrast, the same nanoplates with 7 X 7 reconstructed {111} surfaces are elastically softer than bulk. On {100} surfaces, the 2 X 1 surface reconstruction has little impact. The bond chains are along one of the two <110> directions, making the two <110> directions nonequivalent. The alignment of the bond chains on the opposite surfaces of a nanoplate dictates its elastic anisotropy. The sensitivity of nanoplate elasticity on details of surface atomic arrangements may impact the application of nanoplates (or nanocantilevers) as sensors.