Vacancy ordering transitions in one-dimensional lattice gas with Coulomb interactions - art. no. 045405

Recently, physical properties of single crystals of quasi-one-dimensional s ulfide KCu7-xS4 have been studied. These measurements show several anomalie s, in which the "transition" temperatures and physical properties depend st rongly on x. It was suggested that these transitions are most likely due to vacancy ordering involving Cu+-ion diffusion along the Cu(2)-Cu(2) zigzag chains. In this paper we propose a long-range mean-field method to study va cancy ordering in a one-dimensional chain with 1/r. Coulomb interactions. O ur results indicate that phase transitions exist in a one-dimensional latti ce gas system in which vacancy ordering is involved. The system has complex thermodynamic properties which are extremely sensitive to the occupancy. E ach simple rational occupancy has a unique phase diagram.