Nature of the spin-singlet ground state in CaCuGe2O6

We investigate by means of ab initio electronic structure analysis and Quantum Monte Carlo calculations the scenario where longer-ranged magnetic interactions dominate over short-ranged interactions in the physical description of compounds. This question is discussed, in particular, for the case of CaCuGe${}_2$O${}_6$ which shows a spin-singlet behavior induced by third nearest neighbor copper pairs.