Phase Transitions in the Planar Hard Triangle System
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Date
2020-02-02
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Addis Ababa University
Abstract
A 2D liquid crystal system composed of hard particles shows phase transitions as the
pressure of the system varies. This fact was con_rmed by di_erent works done on 2D
liquid crystal system di_erent shapes. These works done on hard particles of di_erent
shapes con_rmed that particles of di_erent shapes show phase transition at di_erent
packing fractions. By understanding this idea, we are interested to study the phase
transition of a system composed of hard triangles. We have considered NPT system with
di_erent number of particles and used Monte Carlo method to study the phase transition
of the system. To study the phase transitions, we have considered the pressure, the
radial distribution function and the mean square displacement of the particles at di_erent
packing fractions. All of these results have shown as there is phase transition at _ _ 0:6
and _ _ 0:9. The packing fraction at which the phase transition occurred didn't vary
with size of the system which shown the phases are stable at the thermodynamic limit. As
shown by previous work, if there is complete isotropic phase, the tetratic order parameter
s4 = 0 [20] but in our case the minimum value of tetratic order parameter was s4 _ 0:41
which shows the non-existence of complete isotropic phase for hard triangles. For a
system of hard triangles, the phases observed during the phase transitions are: isotropic
phase(when _ < 0:6), tetratic phase (when 0:6 < _ < 0:9) and solid phase (when _ > 0:9),
and the plastic crystal wasn't observed.
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Keywords
Phase Transitions, Planar Hard, Triangle System