2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/151764The strong corrugation of the V4O9 layer in the spin gap system CaV4O9 is examined for its impact on the exchange coupling constants between the spin 1/2 V ions. Local spin density (LSD) calculations show that the V spin occupies a d(x^2-y^2) orbital (x and y are the V-V directions). The Kanamori-Goodenough superexchange rules, and the degeneracy of ferromagnetic and antiferromagnetic alignments within LSD, suggest that 2nd neighbor couplings dominate over nearest neighbor, resulting in two coupled S=1/2 metaplaquette systems.4 pages in 2-column form, 5 figuresStrongly Correlated ElectronsMaterials Sciencetext