Deterministic Large-Scale Simulations of the Low-Dimensional Magnetic Spin Systems

Two types of deterministic simulation techniques are presented and applied to a class of the real low-dimensional magnetic systems described by the Heisenberg hamiltonian which includes the macroscopic Haldane-gap and molecular-based spin S=1 chains, small size magnetic clusters embedded in some supramolecules and other compounds. Using both the exact diagonalization and the transfer-matrix techniques, the spin degrees of freedom are accurately taken into account, yielding the energy spectra and the thermodynamical functions. It is shown that our modelling tool based on our own codes and recent parallelization/vectorization mechanisms is reliable and leads to a quntitative agreement with experiment. We review the results for some isotropic and anisotropic systems, for systems with uniform and non-uniform interactions and those with antisymmetric interactions.