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First-Principles Study on Preferential Energetics of Mg-based Ternary Alloys Revisited by Short-Range Order in Disordered Phases

To investigate the formation of Mg-based long-period stacking ordered (LPSO) structure, we systematically study the preference of the short-range order (SRO) in metastable disordered phases of Mg-RE-Zn (RE = Y, La, Er, Ho, Dy, Tb) and Mg-Gd-Al ternary alloy systems through first-principles calculation. RE-Zn (RE = Y, Er, Ho, Dy, Tb) and Gd-Al pair clusters' probability showed the tendency of increasing. In contrast, La-Zn pair clusters' probability is not increasing, whose system dose not form LPSO structure. This preference of SRO in disordered phases of Mg-based ternary alloys certainly indicates that peculiar L12-type ordering in LPSO as well as possibility of LPSO formation should have strong correlation with SRO tendency of energetically competitive disordered phases.