On phase diagrams for Au-Si nanosystems: thermodynamic and atomistic simulations

Abstract

Phase diagrams for Au-Si nanosystems were calculated by using thermodynamic simulation (NANOCALPHAD methodology) and molecular dynamics (MD). Thermodynamic simulations have been carried out for two Au-Si nanosystems: (i) a solid (crystalline) Si or Au nanoparticle (NP) contacting with an Au-Si nanodroplet of the same radius; (ii) a cylindrical Si nanowire (nanowhisker) with an Au-Si nanodroplet on its butt. We have found that the eutectic temperature of the first system decreases in comparison with the bulk eutectic temperature, and the position of the eutectic point slightly shifts to a lower value of the molar fraction of Si that agree with MD results obtained on another system, i.e. on spherical Au-Si NPs. Contrary to the first system, the eutectic temperature of the second one, i.e. of the system “Si nanowhisker -- Au-Si nanodroplet” increases in comparison with the bulk phase diagram. An explanation of such a result is proposed and discussed.