Equation of state for ''classical'' helium

A classical base-line equation of state for fluid helium is calculated from a recent accurate pair potential and a classical statistical-mechanical theory. The range covered is 2.5--1400 K and densities up to 90 mol/dm3. Comparison with experimental data shows how quantum effects in 4He behave in the dense-fluid region. A pseudoclassical calculation based on experimental second virial coefficients fails to account for the high-density quantum effects. The volume expansion caused by zero-point motion can be directly seen in the curvature of the Zeno line