Nanoplate elasticity under surface reconstruction

Abstract

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 7×7 and 2×1 reconstructions. Nanoplates with unreconstructed {111} surfaces are elastically stiffer than bulk. In contrast, the same nanoplates with 7×7 reconstructed {111} surfaces are elastically softer than bulk. On {100} surfaces, the 2×1 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.