Thermodynamic stability of nanometre-sized Cu₃Au systems

Classical molecular dynamics simulations have been used to investigate the order-to-disorder transition in bulk and nanometre-sized Cu₃Au systems. The Helmholtz free energy difference between ordered and disordered phases was evaluated at different temperatures through the Bennett's method. The change of free energy differences with temperature was employed to identify the transition temperatures. The obtained information was used to study the dynamics of a nanometre-sized Cu₃Au particle in a He gas thermostat at the transition temperature. It is shown that the system underwent rapid fluctuation in the chemical order degree related to the formation of vacancies and of atoms with defective coordination. Additional information on surface energies was also gained through a thermodynamic description of the transition process.