A computational exploration of 4F6T orthoconic antiferroelectric liquid crystal and its fluorinated derivatives for enhanced nonlinear optical characteristics

Orthoconic antiferroelectric liquid crystals (OAFLCs) are a class of materials with exceptional optoelectronic potential, particularly due to their bistable switching behavior, thermal stability, and inherent nonlinear optical (NLO) properties. However, the effects of fluorination on the properties of the liquid crystalline compound 4F6T, a member of the OAFLC family, for enhanced nonlinear optical (NLO) performance have yet to be explored. This study aims to address this by investigating the properties of 4F6T and its fluorinated derivatives using a computational model, where a single molecule is analyzed by treating it analogous to an ideal gas molecule. Exploiting the computational power of density functional theory (DFT) with the B3LYP functional and the 6–311G(d,p) basis set, which includes the polarization function, that is essential for fluorine molecules, we systematically explored the impact of fluorination on molecular stability, thermodynamics, electronic structure, vibrational characteristics, and NLO behavior. Fluorination was found to enhance molecular stability, with the zero-point vibrational energy (ZPVE) decreasing from 459.20 kcal/mol (4F6T) to 438.65 kcal/mol (4F6T(2,3,2′,3′F)). The dipole moment increased significantly, reaching a maximum of 6.46 Debye for the fully fluorinated derivative. Notably, the partially fluorinated derivative 4F6T(2,3F) demonstrated the highest hyperpolarizability (β₀ = 7970.69 a.u.) and superior NLO performance. These fluorinated molecules have significant use in modern fast-response displays. Our findings indicate that the 4F6T(2,3F) molecule is most suitable for photonic and optoelectronic applications.