Coupled cluster treatment of an interpolating triangle-kagomé antiferromagnet

The coupled cluster method (CCM) is applied to a spin-half model at zero temperature which interpolates between a triangular lattice antiferromagnet (TAF) and a kagomé lattice antiferromagnet (KAF). The strength of the bonds which connect kagomé lattice sites is J, and the strength of the bonds which link the non-kagomé lattice sites to the kagomé lattice sites on an underlying triangular lattice is J′. Our results are found to be highly converged, and our best estimate for the ground-state energy per spin for the spin-half KAF (J′ = 0) is -0.4252J. The amount of classical ordering on the kagomé lattice sites is also considered, and it is seen that this parameter goes to zero for values of J′ very close to the KAF point. Further evidence is also presented for CCM critical points which reinforce the conjecture that there is a phase near to the KAF point which is very different to that near to the TAF point (J = J′).