An interaction-round-a-face density-matrix renormalization-group (IRF-DMRG) method is developed for higher integer spin chain models which are rotational invariant. The expressions of the IRF weights associated with the nearest-neighbor spin-S interaction ${ \bf S}_{ i} \cdot { \bf S}_{ i+1}$ are derived explicitly. Using the IRF-DMRG with these IRF weights, the Haldane gaps $\Delta$ and the ground state energy densities $e_{ 0}$ for both S=1 and S=2 isotropic antiferromagnetic Heisenberg quantum spin chains are calculated by keeping up to only m=90 states.
Categories: cond-mat.stat-mech