Spin-density wave, charge density wave, and polarizabilities of C60 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 Mo/ller–Plesset correction in second order, a linear polarizability of 325.5 a.u. and a second hyperpolarizability of 5.87×10−36 esu are found.