First-Principles Study of Phase Equilibria in the Ni-Cr System
The relative importance of various free energy contributions to phase stability in the Ni-Cr system is investigated using total energy calculations in the local density approximation combined with the cluster expansion and the cluster variation method. In particular, we develop a formalism to calculate the vibrational free energy in disordered alloys exhibiting short-range order. The methodology is well adapted to be used in conjunction with first-principles total energy calculations. It is found that the coupling between configurational and displacive degrees of freedom is crucial for the accurate description of the equilibrium phase diagram of the Ni-Cr system, with electronic excitations playing a less important role and the effects of short-range order being essentially negligible.
KeywordsBulk Modulus Electronic Excitation Equilibrium Phase Diagram Total Energy Calculation Force Constant Matrix
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