Pseudo-second-order-phase-transition temperature

Pseudo-second-order-phase-transition temperature 

For simplicity, assume that vab is the geometrical mean of va and vb, i.e., the Berthelot law, and extend the free energy derived from Equation 2.f22 in the power series of Sa and, S),. The zero determinant of the quadratic coefficients gives the pseudo-second-phase-transition temperature as follows 

In the second-order approximation of the free energy, above T, Sa and Sb are both zero. Below T, the order parameters are non-zero. At T, the quadratic terms vanish. This formula illustrates the pseudo-second-phase-transition temperature vs. the molecular parameters that shows the same shapes as those of the numerical calculations of the N-I transition temperature Tc, mentioned above. 

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The first term in the formula is the pseudo second order phase transition temperature T. The coefficient B is not great, therefore the second term is not significant. The difference of Tc and T is small, experimentally only a few degrees difference. 

Pseudo-second-order-phase-transition temperature... 

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