  We apply density functional theory band structure calculations, the
coupled-cluster method, and exact diagonalization to investigate the
microscopic magnetic model of the spin-1/2 compound Cu2GeO4. The model is
quasi-two-dimensional, with uniform spin chains along one direction and
frustrated spin chains along the other direction. The coupling along the
uniform chains is antiferromagnetic, J 130 K. The couplings along the
frustrated chains are J1 -60 K and J2 80 K between nearest neighbors and
next-nearest neighbors, respectively. The ground state of the quantum model is
a spiral, with the reduced sublattice magnetization of 0.62 mu_B and the pitch
angle of 84 deg, both renormalized by quantum effects. The proposed spiral
ground state of Cu2GeO4 opens a way to magnetoelectric effects in this
compound.
