Ground-state analysis of ordered superstructures in the basal plane of YBa2Cu3Oz

Abstract

Ordered superstructures consisting of occupied and empty oxygen sites in the Cu-O basal plane of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{\mathrm{z}}$ have been determined. Pairwise interactions ($V_1$, $V_2$, $V_3$) between nearest- and next-nearest-neighbor sites are assumed and ordering maps are plotted as a function of $V_2$/$V_1$ and $V_3$/$V_1$ (in the ordering case: $V_1$>0). The ground state of this Ising model is determined by a direct enumeration method and the relation with experimentally obtained structures is discussed.