The molecular structure and dihedral angle and effect on some liquid crystal phases using the density-functional theory

الملخص EN

Computer simulations provides a powerful tool for the investigation of liquid crystalline phases.

In this work, the ability of simulations to accurately calculate the values of material parameters of liquid crystal molecules is investigated.

A geometry optimization for liquid crystal molecules is performed using density functional theory DFT-B3LYP/6-311G (d,p) calculations on Schiff’s bases substituted with polar groups Cl, Br, F, I, NO2, CH3, OCH3 and COCH3 in para position or aniline moiety molecules, which encompass key structural features of a range of common liquid crystalline molecules.

Molecular quantum mechanical simulations of these 'fragment' molecules are carried out in the liquid crystal phase to investigate correlations between dihedral angles and liquid crystal’s Smectic and Nematic phases.

Density electronic distribution effect is also studied.

The study of geometry and especially the value of the dihedral angle for core of molecule and phases showed the effect of the dihedral angle value to specify the type of the phase (Smectic or Nematic) for molecules in liquid crystals studied.

Molecules that gave the Nematic phase had dihedral angle larger than those that showed Smectic phase for molecules in liquid crystals studied.