Entropy driven formation of Smectic C in system of Zig-zag shaped molecules

TL;DR

This study uses Monte Carlo simulations to demonstrate that the shape of zig-zag molecules alone can induce the formation of Smectic C phases over a range of angles, highlighting the role of steric interactions.

Contribution

First conclusive evidence that molecular shape alone can induce SmC phase in zig-zag molecules through steric interactions.

Findings

SmC phase observed for zigzag angles between 35° and 80°

Transition from tilted to non-tilted crystal for smaller angles

Steric interactions from molecular shape induce SmC formation

Abstract

We have carried out Monte Carlo simulations of zig-zag shaped molecules where the the molecules is composed of three rigidly linked hard spherocylinder arranged in a zigzag fashion. By varying zigzag angle we have mapped out the whole phase diagram as a function of pressure, molecular density and zigzag angle $\Psi$. For $\Psi$ between $35^0$ and $80^0$ our model simulation exhibits SmC phase. This is the first conclusive evidence where steric interaction arising out of molecular shape alone induce the occurrence of SmC phase for a wide range of zigzag angle. For smaller $\Psi$, a transition from tilted crystal (XT) to nontlted crystal is observed.