Simple derivation of the frequency dependent complex heat capacity

TL;DR

This paper provides a straightforward derivation of the frequency-dependent complex heat capacity, emphasizing its origin in non-equilibrium behavior near thermodynamic equilibrium during temperature modulation experiments.

Contribution

It offers a simplified derivation of the complex heat capacity expression, clarifying its relation to non-equilibrium phenomena in thermodynamic systems.

Findings

The complex heat capacity arises from non-equilibrium effects.

The derivation clarifies the physical origin of the frequency dependence.

It emphasizes the role of slow internal degrees of freedom.

Abstract

This paper gives a simple derivation of the well-known expression of the frequency dependent complex heat capacity in modulated temperature experiments. It aims at clarified again that the generalized calorimetric susceptibility is only due to the non-equilibrium behaviour occurring in the vicinity of thermodynamic equilibrium of slow internal degrees of freedom of a sample when the temperature oscillates at a well determined frequency.