Study of properties of gold–iron alloy in the macro- and nanocrystalline states under different $P$–$T$ conditions

Parameters of the Mie–Lennard-Jones pair interatomic potential for a disordered substitutional fcc-Au–Fe alloy are determined. The concentration dependences of the lattice properties of a macrocrystal of this alloy are calculated based on these parameters. The results of calculating twenty properties of fcc-Au, fcc-Fe, and fcc-Au$_{0.5}$Fe$_{0.5}$ macrocrystals showed good consistency with the experimental data. The equation of state $P(\nu,T;N)$ and baric dependences of both the lattice and surface properties of the fcc-Au$_{0.5}$Fe$_{0.5}$ alloy are calculated using the RP nanocrystal model. The calculations have been performed at temperatures $T$ = 100, 300, and 500 K for both the macrocrystal $(N=\infty)$ and the cubic nanocrystal consisting of $N$ = 306 atoms. It is shown that, during isothermal–isobaric $(P=0)$ decrease in the nanocrystal size, its Debye temperature, elastic modulus, and specific surface energy decrease, while its specific volume, coefficient of thermal expansion, specific heat, and Poisson ratio increase. At low temperatures, the specific surface energy increases in a certain range of pressures with an isothermal–isobaric decrease in the number of atoms in the nanocrystal. This range of pressures disappears with an increase in temperature.