Finite-temperature characterization and simulations of the molecular assemblies Mn_6 and Ni_(12)

摘要

Numerical transfer-matrix approach and exact diagonalization technique exploiting the point-group symmetry and the properties of the shift operator are worked out in the framework of quantum statistical mechanics for the isotropic Heisenberg spin Hamiltonian with the ring geometry. They are applied in large-scale simulations to the title high nuclearity cyclic clusters Mn_6 (i.e. [Mn(hfac)_2NITPh]_6) and Ni_(12) (i.e. Ni_(12)(O_2CMe)_(12)(chp)_(12)(H_2O)_6(THF)_6) in order to model quantitatively their magnetic properties. For Ni_(12) complex new experimental susceptibility data are also reported. New microscopic spin model parameters for both molecules are obtained from a fit of the theoretical susceptibility curves to the experimental results.