Eur. Phys. J. B 23, 183-189 (2001)
https://doi.org/10.1007/s100510170067

Finite-temperature characterization and simulations of the molecular assemblies Mn₆ and Ni₁₂

¹ Computational Physics Division, Institute of Physics, A. Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland
² Institute of Technology, Pedagogical University in Zielona Góra, Poland
³ Dipartimento di Scienze Fisiche, Università di Napoli, Piazzale Tecchio, 80125 Napoli, Italy and INFM Unità di Napoli, Italy
⁴ Dipartimento di Scienze Fisiche, Università di Napoli, Complesso Universitario di Monte S. Angelo, 80125 Napoli, and INFM Unità di Napoli, Italy
⁵ Dipartimento di Chimica, Università di Firenze, via Maragliano 77, 50144 Firenze, Italy

Corresponding author: ^a filippo.esposito@na.infn.it

Received: 11 May 2001
Revised: 24 July 2001
Published online: 15 September 2001

Abstract

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 Mn₆ (i.e. [ Mn(hfac)₂NITPh] ₆) and Ni₁₂ (i.e. Ni₁₂(O₂CMe)₁₂(chp)₁₂(H₂O)₆(THF)₆) in order to model quantitatively their magnetic properties. For Ni₁₂ 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.