An approximate value for the ground-state energy of an antiferromagnetic lattice of spins one-half is determined by means of a repeated renormalization procedure in which the lattice is divided into cells with an effective interaction. This effective interaction is determined on the basis of the spin-hamiltonian formalism.
van de Braak, H. P., Caspers, W. J., de Lange, C., & Willemse, M. W. M. (1977). The determination of the ground-state energy of an antiferromagnetic lattice by means of a renormalization procedure. Physica A, 87(2), 354-368. https://doi.org/10.1016/0378-4371(77)90022-X