Inversion of the First Nearest Neighbor Interchange Interaction Potential in L12 Structure by Microscopic Phase-Field Simulation

Based on the microscopic phase-field theory, the inversion formula of the connection between the first nearest neighbor interchange potential W-1 and the long range order parameter eta, i.e. -4W(1).eta/k(B)T = ln (1 - eta)[1 - c(1 + 3.eta)]/(1 + 3.eta)[1 - c(1 - eta)] was concluded according to the formula for the connection between occupation probability and free energy by Khachaturyan. According to the formula, W-1 of L1(2) structure can be simply calculated under different conditions of atomic concentration and temperature only by substituting the temperature and atomic concentration of L-1 structure transformation point. The calculated result is close to the numerical value by first-principle and other methods. At the same time, it is found that W-1 of L1(2) structure was affected by atomic concentration and temperature in the phase diagram range of precipitated L1(2).