Microsecond-scale observation of phase transition and diffusion in 5CB liquid crystal at the molecular level

Abstract

Molecular dynamics methods have proven their applicability for the simulation of the structure and properties of liquid crystals. For the reproduction of phase transitions in liquid crystals, many authors have reparameterized the classical force fields. For the first time, we demonstrate that even a general-purpose force field, for example, General AMBER Force Field (GAFF), without modifications is also capable of reproducing an isotropic–nematic transition at 300 K within microsecond-scale simulations. However, the isotropic–nematic transition enthalpy is overestimated, which leads to higher thermodynamic stability of the nematic phase. For the obtained nematic phase, the calculations of self-diffusion are performed during almost 2 μs at different temperatures, which are compared against previous experimental and computational studies. The diffusion coefficients are underestimated compared with the experiment because of stronger molecular interactions. The diffusion anisotropy ratio lies within the experimental observations. Our work justifies the key problems of GAFF in reproducing the properties of the 5CB liquid crystal.