Quantum Corrections to the Coexistence Curve of Neon near the Triple Point

Quantum corrections to the free energy of a classical Lennard-Jones system are calculated, using the well-known Wigner expansion in powers of . In the vicinity of the triple point of neon, the ⁴ term turns out to be about 40 times smaller than the ² term, which justifies trunction of the series after the first correction term. The resulting changes in the densities and pressures of melting and condensation transitions give rise to a phase diagram which is in good agreement with experimental neon results.