The Mayer f-function is an auxiliary function that often appears in the series expansion of thermodynamic quantities related to classical many-particle systems. It is named after chemist and physicist Joseph Edward Mayer.
Consider a system of classical particles interacting through a pair-wise potential
where the bold labels and denote the continuous degrees of freedom associated with the particles, e.g.,
for spherically symmetric particles and
for rigid non-spherical particles where denotes position and the orientation parametrized e.g. by Euler angles. The Mayer f-function is then defined as
where the inverse absolute temperature in units of energy<sup>âÂÂ1</sup> .