Theory of quantum-mechanical effects on the thermodynamic properties of Lennard-Jones fluids

In this paper we consider the problem of computing the quantum-mechanical corrections to the thermodynamic properties of systems whose two-particle interaction may be described by a Lennard-Jones 6-12 potential. Using a procedure first developed by Feynman, together with physical arguments, we develop an effective two-particle 6-12 potential which includes quantum-mechanical corrections. Using this potential in conjunction with the theory of corresponding states we compute the quantum effects on: (i) the second virial coefficient, (ii) the critical-point location, (iii) the surface tension, (iv) the critical-point amplitudes and exponents, (v) the correction to scaling amplitudes and exponents, (vi) the liquid-gas and solid-liquid phase boundaries, and (vii) the Debye temperature at the melting point. In all cases there is good qualitative and frequently quantitative agreement with experimental results. The theory is limited to "high temperatures" since exchange effects are not included.