Changes of the Thermodynamic Properties at Isochoric and Isobaric Decrease of the Silicon Nanocrystal Size

Abstract

Equation of state P(ν/ν_o) and the baric dependences of the lattice and surface properties of silicon macro- and nanocrystals have been calculated using the method of calculation of crystal properties from the pair Mie–Lennard-Jones interatomic potential and the RP-model of nanocrystal. The isothermal dependences of P(ν/ν_o) for the macro- and the nanocrystal are shown to be intersected at a certain value of relative volume (ν/ν_o)₀. The surface pressure becomes zero at the intersection point (at (ν/ν_o)₀). The value of (ν/ν_o)₀ decreases upon isomorphic–isomeric increase in temperature and also at isomorphic–isothermic decrease in the number of atoms N in the nanocrystal, or at isomeric–isothermic deviation of the nanocrystal shape from the most energetically optimal shape (in the RP-model, this shape is a cube). The obtained equation of state is used to study the changes of the silicon properties at isochoric (ν/ν_o = 1) and also isobaric (P = 0) decrease in N at temperatures 300 and 1000 K.