Non-additive quantum corrections to the virial coefficients

Non-additive contribution to the first quantum correction to the fourth virial coefficient is derived; the result is exact at the level of graphs with at most two triplet potentials. Values of non-additive quantum corrections to the third and fourth virial coefficients are given for a Lennard-Jones and realistic pair-potential functions.

Neglecting non-additive quantum corrections to the fourth virial coefficient of methane exaggerate these corrections between T/[K] ⩽180, but under estimate them at higher temperatures. It would be impossible to calculate accurate fourth virial coefficient on the basis of the above assumption in the region 155 < T/[K] ⩽ 165.