  We generalize the imaginary chemical potential quantum Monte Carlo (QMC)
method proposed by Dagotto et al. [Phys. Rev. B 41, R811 (1990)] to systems
without particle-hole symmetry. The generalized method is tested by comparing
the results of the QMC simulations and exact diagonalization on small Hubbard
molecules, such as tetrahedron and truncated tetrahedron. Results of the
application of the method to the C$_{60}$ Hubbard molecule are discussed.
