Effect of alloying elements on in-plane ordering and disordering of solute clusters in Mg-based long-period stacking ordered structures: A first-principles analysis

Using density functional theory, we characterized the in-plane binding between L12-type solute clusters in Mg–M–RE (M = Al, Zn; RE = Y, Gd) long-period stacking ordered (LPSO) structures. The difference between the Al and Zn concentrations within the clusters determines whether the intercluster interaction is attractive or repulsive. Incomplete in-plane ordering observed experimentally in Mg–Zn–Y LPSO structures was suggested to be caused by the unlinked nature of the clusters owing to their significant inward contraction.