Atomistic Simulation of Thermoinduced Structural Transformations in Four-Component Cu–Au–Pt–Pd Nanoalloys with Different Morphologies

The article presents the results of the molecular dynamics simulation performed for thermoinduced structural transformations in four-component Cu–Au–Pt–Pd nanoalloys using the tight-binding potential. The following configurations have been chosen as initial ones: a core–shell (Cu₂₀₀–Au₆₀₀–Pt₈₀₀)@Pd₂₄₀₀ system, in which the core is a multicomponent alloy with uniformly distributed components; an onion-like Cu₂₀₀@Au₆₀₀@Pt₈₀₀@Pd₂₄₀₀ structure, a Cu₂₀₀–Au₆₀₀–Pt₈₀₀–Pd₂₄₀₀ alloy with a uniform distribution of the components, and Janus structures with asymmetric (Cu₂₀₀/Au₆₀₀/Pt₈₀₀/Pd₂₄₀₀) and symmetric (Cu₁₀₀/Au₃₀₀/Pt₄₀₀/Pd₂₄₀₀/Pt₄₀₀/Au₃₀₀/Cu₁₀₀ and Pd₁₂₀₀/Pt₄₀₀/Au₃₀₀/Cu₂₀₀/Au₃₀₀/Pt₄₀₀/Pd₁₂₀₀) distributions of the components. The analysis of the temperature dependences of the potential component of the internal energy has been employed to determine the temperatures corresponding to the onset of the melting–crystallization phase transition and to estimate the value of the temperature hysteresis. The regularities have been found for variations in these values as depending on the thermal action rate. The regularities of the structure formation have been analyzed, the dominating role of the local fcc environment has been revealed, and the cases of the formation of other crystalline structures (hcp and bcc) have been observed. The regularities of chemical segregation have been described confirming that different scenarios of the segregation behavior of the components may take place. An original technique has been used to estimate the specific surface energy for multicomponent metal nanoparticles (final configurations resulting from a cycle of a thermal action including the melting–crystallization phase transitions). The values of the specific surface energy correlate with the stability of the final configurations corresponding to different initial configurations.