The partition function for an atom in a monatomic liquid is evaluated by assuming that the atom is constrained by its nearest neighbors to move in a spherical region, and that the potential energy of the atom at any point within this region can be found if the law of force between two atoms is known. On the basis of this partition function an expression for $C_v$ is derived. The theory is checked by a comparison of the experimental and theoretical values of $C_v$ for liquid argon.

• Received 17 April 1939

DOI:https://doi.org/10.1103/PhysRev.56.926