Determination of heisenberg exchange coupling constants in clusters with magnetic sites: A local spin approach

Abstract

This work studies the ability of the two-center local spin quantities, provided by the partitioning of the expectation value of the spin-squared operator <Ŝ2> corresponding to N-electron systems, for determining spin-exchange coupling constants within the Heisenberg spin Hamiltonian model. The spin-exchange parameters, which characterize this Hamiltonian for a determined system, have been evaluated in the HeH2 aggregate and in several Hn clusters (n = 2, 3, 4) with different geometrical arrangements, using internuclear distances larger than the equilibrium ones (beyond the bonding regions). The results found have been analyzed and compared with those arising from other approaches, showing the feasibility of our methodology. © 2014 Wiley Periodicals, Inc. The partitioning of the values of a determined molecular property into contributions assigned to atoms, or groups of atoms, in N-electron systems is a useful tool in molecular physics and quantum chemistry. The two-center contributions arising from the partitioning of the spin-squared operator expectation value can be used for determining the coupling constants within the Heisenberg spin Hamiltonian model. This conceptually simple and computationally suitable approach performs well against more sophisticated methods. Copyright © 2014 Wiley Periodicals, Inc.