Analysis of the specific heat and the free energy of [N(CH₃)₄]₂ZnBr₄ close to the ferro-paraelastic phase transition

ABSTRACT

A power-law formula deduced from the Ising model was used to analyze the temperature dependence of the specific heat $C_p$ and the Gibbs free energy $G$ of [N(CH₃)₄]₂ZnBr₄ compound in the vicinity of the phase transition temperature of T_C= 287.2 K. Obtained values of the critical exponents $\alpha$ from the Gibbs free energy were consistent with that predicted from 2-d potts model ($\alpha$ = 0.3), while obtained values of $\alpha$ from the specific heat in both ferroelastic and paraelastic phases were consistent with that predicted from the mean field theory ($\alpha$ = 0) in the vicinity of the phase transition temperature. This is an indication of that [N(CH₃)₄]₂ZnBr₄ compound undergoes a second order type phase transition.

Also, the enthalpy ($H$) and the entropy ($S$) of this crystal were calculated in terms of the extracted values of the critical exponent in both ferroelastic and paraelastic phases.

KEYWORDS:

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

ORCID

A. Kiraci http://orcid.org/0000-0003-4067-1004