SPIN-DENSITY WAVE, CHARGE-DENSITY WAVE, AND POLARIZABILITIES OF C-60 IN THE PARISER-PARR-POPLE MODEL

The Pariser-Parr-Pople Hamiltonian is investigated on a single C60 molecule in the Hartree-Fock approximation. The effect of on-site and two-site electron-electron interactions on the stability of states other than the normal paramagnetic state is studied. In particular (i) a spin-density wave state, with a structure similar to that of the classical ground state of the antiferromagnetic Heisenberg Hamiltonian; and (ii) a charge density wave state which occurs for weakly screened two-site interactions. Linear and nonlinear optical properties are also calculated. With the finite field method and the Moller-Plesset correction in second order, a linear polarizability of 325.5 a. u. and a second hyperpolarizability of 5.87 X 10(-36) esu are found.