Quantum corrections to the classical pressure are obtained for Lennard-Jones models of argon, neon, and helium using classical Metropolis algorithm computer simulations. The corrections for non-commutativity are obtained to fourth order in Planck's constant. Compared to the classical virial pressure on all isotherms at liquid-like densities, the quantum correction is found to be ${\cal O}(10^{-2})$ for argon, ${\cal O}(10^{0})$ for neon, and ${\cal O}(10^{3})$ for helium. The first order correction due to wave function symmetrization is also obtained, but this is relatively negligible.
Comment: 15 pages, 9 figures