Microscopic degrees of freedom for a solid/liquid:
At high temperatures where all vibrational degrees of freedom in a solid/liquid are thermodynamically active the specific heat is also simply given by counting degrees of freedom:
The six degrees of freedom are three from translation and three from vibrational degrees of freedom along each of three Cartesian directions in the solid state. The _expression is traditionally called Dulong-Petit's law. Note that for solids as well as liquids it is not important to distinguish between and since there is so little thermal expansion of a solid or liquid when heated at constant pressure that the amount of work performed in expanding against the atmosphere can be neglected. |
