Origin of long-period superlattices in Ag-Mg alloys

Abstract

We have calculated the electronic structures and the relative stabilities of ${\mathrm{Ag}}_3$Mg, assuming the ${\mathit{L}}_{12}$, ${\mathit{DO}}_{22}$, and ${\mathit{DO}}_{23}$ structures. We provide strong evidence that the formation of the ${\mathit{DO}}_{23}$ structure in particular, and other long-period superlattices in general around the 3:1 stoiochiometry, is driven by the topology of the Fermi surface.