Magnetic couplings in CsV(2)O(5): a new picture.

Concerning its magnetic properties, the layered vanadate CsV(2)O(5) has long been considered as formed by isolated spin-1/2 dimers characterized by a large antiferromagnetic coupling of about 146 K. This interpretation was supported by both magnetic susceptibility measurements and the obvious presence of magnetically active strongly dimerized V(4+) ions. In this work we investigate the magnetic properties of this compound through an extensive use of the broken-symmetry formalism in the framework of density-functional theory. Our calculations demonstrate that the system is built from strongly dimerized alternating chains where the structural and magnetic dimers are distinct from each other.