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

The commensurate-incommensurate phase transition of a Rb₂ ZnCl₄crystal was studied using a conduction calorimeter. By identifying the contribution of the specific heat to the transition enthalpy it was possible to show, for the 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 theoretical predictions for a domain wall model having repulsive-attractive interaction; satisfactory results were obtained for the first time. The same analysis was applied to the normal-incommensurate phase transition and no latent heat was observed, as expected.