Magnetic susceptibility and ground state energy of mMPYNN-BF4

We treat the organic system mMPYNN-BF4 as a network of hexagons. Each hexag on contains six S = 1/2 spins coupled alternately with ferro- and antiferro magnetic interactions. The antiferromagnetic coupling between hexagons is t reated as a perturbation term. We obtain the ferro- and antiferromagnetic c oupling constants in the hexagon and the antiferromagnetic coupling constan t between hexagons. The susceptibility calculated by the second-order pertu rbation method for mMPYNN-BF4 agrees well with the experimental results. Th e ground state energy is also calculated.