A phenomenological study on ferroelectric β-glycine

Abstract

The anomalous behavior of the specific heat for $\beta$-glycine was analyzed in terms of the compressible Ising model approximately 5 K below and above the ferrelectric-paraelectric phase transition temperature of T_C = 252 K. The obtained value of the critical exponent $\alpha \mathrm{ }$= 0.12 in the ferroelectric phase (T < T_C) was consistent with that predicted from the 3-d Ising model ($\alpha \mathrm{ }$= 0.13), while the obtained value of $\alpha \mathrm{ }$= 0.32 in the paraelectric phase (T > T_C) was consistent with that predicted from the 2-d potts model ($\alpha \mathrm{ }$= 0.30). Some thermodynamic quantities such as the internal energy, the entropy and the free energy of $\beta$-glycine were then predicted in terms of these extracted values of the critical exponents close to the phase transition temperature of T_C. Our calculated values of the thermodynamic quantities are in good agreement with the observed data.

Keywords:

• Ising model
• specific heat
• critical exponent
• thermodynamic quantities
• $\beta$-glycine