Phase diagram of a biaxial nematogenic lattice model: A Monte Carlo simulation study

The phase diagram for a lattice system of biaxial molecules possessing $D_{2h}$ symmetry and interacting with the Straley’s quadrupolar pair potential in Sonnet–Virga–Durand parameterization (Sonnet et al., 2003) has been determined using Monte Carlo simulation. Our results confirm that the nematogenic model yields both the uniaxial and biaxial nematic macroscopic phases along with a tricritical point in the transition from uniaxial to biaxial nematics as has been predicted in mean field theory. By analyzing the behavior of a free-energy-like function, derived from the probability distributions of energy, the order of phase transitions is detected. A conclusive numerical evidence in support of the existence of a tricritical point on the uniaxial–biaxial transition line in the phase diagram is reported. Although the nature of the phase diagram is qualitatively identical as obtained in the mean field study however the location of triple point differs significantly from theoretical prediction.