Electronic-structure calculations, the cluster-variation method of statistical mechanics, and the phase-field method were combined in attempted first-principles calculations of phase equilibria and microstructural evolution associated with the disorder-$\mathrm{L}{1}_0$ transition of the Fe-Pt system. The calculated disorder-$\mathrm{L}{1}_0$ transition temperature was within $\sim 10$ K difference from the experimental value, and the locus of spinodal ordering temperature is placed in the phase diagram. The calculated microstructure demonstrates preferential growth of the ordered domain along the <100> direction and, in the later period, an anisotropic morphology of an antiphase domain structure develops. We offered an interpretation from the atomistic point of view for this morphology. We therefore achieved consistent first-principles multiscale calculations of phase equilibria and microstructural evolution, bridging microscopic to mesoscopic scales without any adjusting parameters.

• Received 6 January 2023
• Revised 9 April 2023
• Accepted 11 May 2023

DOI:https://doi.org/10.1103/PhysRevB.107.174111