Analysis of the specific heat and the free energy and calculation of the entropy and the internal energy of [N(CH₃)₄]₂MnBr₄ close to the phase transition

Abstract

The critical behavior of the specific heat and the Gibbs free energy of [N(CH₃)₄]₂MnBr₄ was analyzed using the Ising model close to the phase transition temperature of T_C = 276.5 K. Obtained value of $\alpha$= 0.02 from the Gibbs free energy and from the specific heat approximately 2.0 K and 1.4 K, respectively, below T_C (ferroelastic phase) and also deduced value of $\alpha$= 0.04 from the specific heat approximately 0.3 K above T_C (paraelastic phase) can be compared with that predicted from mean field theory ($\alpha$ = 0). Also, the entropy and the internal energy of this crystal were predicted.

Keywords:

• Ising model
• specific heat
• free energy
• entropy
• [N(CH₃)₄]₂ZnBr₄