Making use of permutation group technique, the eigenvalue problem of Heisenberg spin- 1 / 2 chains can be solved. Especially the ground state of the antiferromagnetic chains can be easily written.
Using (infinite) density-matrix renormalization-group techniques, ground-state properties of antiferromagnetic S=1 Heisenberg spin chains with exchange and single-site anisotropies in an external field are studied. The phase diagram is known to display a plenitude of interesting phases. We elucidate quantum phase transitions between the supersolid and spin-liquid phases as well as the spin-liquid and ferromagnetic phases. Analyzing spin-correlation functions in the spin-liquid phase, commensurate and (two distinct) incommensurate regions are identified.