Study of properties of fcc-Au-Fe alloys in macro- and nano-crystalline states under various P-T-conditions

The parameters of the paired interatomic potential of Mie–Lennard-Jones for a disordered fcc-Au-Fe substitution alloy were determined by the “average atom” analytical method. Based on these parameters, the concentration dependencies of lattice properties for the macro-crystal of this alloy are calculated. Calculations of 20 properties of macrocrystals fcc-Au, fcc-Fe and fcc-Au0.5Fe0.5 have shown good agreement with experimental data., The state equation P(v, T; N) and baric dependences of both lattice and surface properties of the fcc-Au0.5Fe0.5 alloy are calculated, using the RP-model of the nanocrystal. Calculations were performed at temperatures T = 100, 300 and 500 K for both a macrocrystal (N = ∞) and a cubic nanocrystal with N = 306 atoms. It is shown that with an isothermal-isobaric (P = 0) decrease in the size of a nanocrystal, its Debye temperature, elastic modulus, and specific surface energy decrease, while its specific volume, thermal expansion coefficient, specific heat capacity, and Poisson's ratio increase. At low temperatures in a certain pressure region, the specific surface energy increases with an isothermal-isobaric decrease in the number of atoms in the nanocrystal. As the temperature increases, this pressure region disappears. [Display omitted] •A new method for calculating the properties of a binary alloy is proposed.•The method was tested both for the fcc-Au-Fe alloy and for fcc-Au and fcc-Fe.•By means of this method many properties were obtained the first time.•This method was generalized to the case of a free-standing nanocrystal.•At first time size dependences of properties of Au–Fe nanocrystal were calculated.