Key points are not available for this paper at this time.
The ground state energy and pair correlations have been computed exactly for the spin Formula: see text XY magnet and isotropic Heisenberg antiferromagnet, for a sequence of finite cells on the square and honeycomb lattices. Precise estimates of the ground state energy of the infinite lattices are obtained by extrapolation. It is predicted that the XY magnet has a non-zero transverse magnetization and the Heisenberg antiferromagnet has a non-zero staggered magnetization in the ground state.
Oitmaa et al. (1978) studied this question.