Correlation effects in fullerene molecule

Summary form only given. The fullerene molecule is considered in a framework of Hubbard model. The variational Monte-Caplo (VMC) method is used to calculate expectation values. As a variational wave function we use multideterminant Gutzwiller function. The purpose of this work is to study electronic structure of neutral molecule and its ions for intermediate and strong correlation. It is shown that VMC calculations give ground state and pairing energies which are somewhat different from results obtained by the perturbation theory. For neutral molecule we study strong, coupling limit when Hubbard model is reduced to antiferromagnetic Heisenberg Hamiltonian (AFH). As it was known this model on truncated icosahedron has exotic magnetic ground state in classical approximation. We study ground state of AFH and propose new variational function giving ground state energy which is considerably lower than classical value. We calculate, spin correlation function and establish spin structure of this state.