Microscopic model for the frustrated Cu II-spin tetrahedron-based Cu₄Te₅O₁₂X₄ (X=Cl, Br) systems

Abstract

We present a microscopic study of the electronic and magnetic properties of the recently synthesized spin tetrahedron system Cu₄Te₅O₁₂Cl₄ based on density functional calculations and on ab initio-derived effective models. In view of these results, we discuss the origin of the observed differences in behavior between this system and the structurally similar Cu₂Te₂O₅Cl₂. Since the Br analog of the title compound has not been synthesized yet, we derive the crystal structure of Cu₄Te₅O₁₂Br₄ by geometry optimization in an ab initio molecular dynamics calculation and investigate the effect of substituting Cl by Br. The possible magnetic behavior of Cu₄Te₅O₁₂Br₄ in comparison with the recently studied Cu₂Te₂O₅Br₂ is also discussed.