Evidence of latent heat in the Rb2ZnCl4 commensurate-incommensurate phase transition

The commensurate-incommensurate phase transition of a Rb2ZnCl4 crystal was studied using a conduction calorimeter. By identifying the contribution of the specific heat to the transition enthalpy it was possible to show, for t he first time for a compound of this type, transition latent heat. This was estimated to be Q = 2.3 J mol(-1). The result was compared with theoretica l predictions for a domain wall model having repulsive-attractive interacti on; satisfactory results were obtained for the first time. The same analysi s was applied to the normal-incommensurate phase transition and no latent h eat was observed, as expected.