arXiv subjects

Go Watanabe

Publications and source records attributed to Go Watanabe.

4 recordsLinked to original sources

arXiv2025

Sergeants and Soldiers in Chiral Nematic Liquid Crystal

This study explores the mechanisms behind the helical structures in cholesteric liquid crystalline (CLC) phases using molecular dynamics simulations. By adding chiral agents to the nematic liquid crystalline (NLC) compound, 5CB, the research examines how the shape and motion chirality of the agents influence the overall twisting behavior. The results show that chiral agents induce shape chirality in the 5CB molecules, but dynamic chirality is not detectable at this stage. The study suggests that equilibrium is required for motion chirality to become evident, highlighting the need for further investigation.

cond-mat.soft↗

arXiv2025

Reflection of Phase Anisotropy on Molecule

This study explores how molecular shape changes influence the phase behavior of liquid crystals, particularly the nematic (N) phase of 5CB, through all-atom molecular dynamics (MD) simulations. The results demonstrate that molecular shape anisotropy increases in the N phase, with molecules adopting more elongated conformations as aggregation occurs. We find that the shape distribution is temperature- and aggregation-dependent, and the molecular shape relaxation time is longer in the N phase compared to isolated molecules. Additionally, the study proposes a revision to Onsager and Maier-Saupe theories, considering molecular shape distribution changes, which could improve the explanation of the N-I phase transition in liquid crystals. These findings contribute to a better understanding of the molecular behavior in liquid crystalline phases.

cond-mat.soft↗

arXiv2024

Atomistic analysis of nematic phase transition in 4-cyano-4$^{\prime}$-$n$-alkyl biphenyl liquid crystals: Sampling for the first-order phase transition and the free-energy decomposition

Molecular dynamics (MD) simulations were conducted using the generalized replica exchange method (gREM) on the 4-cyano-4$^{\prime}$-$n$-alkylbiphenyl ($n$CB) system with $n=5$, 6, 7, and 8, which exhibits a nematic-isotropic (NI) phase transition. Sampling near the phase transition temperature in systems undergoing first-order phase transitions, such as the NI phase transition, is demanding due to the substantial energy gap between the two phases. To address this, gREM, specifically designed for first-order phase transitions, was utilized to enhance sampling near the NI phase transition temperature. Free-energy calculations based on the energy representation (ER) theory were employed to characterize the NI phase transition. ER evaluates the insertion free energy of $n$CB molecule for both nematic and isotropic phases, revealing a change in the temperature dependence across the NI phase transition. Further decomposition into intermolecular interaction energetic and entropic terms shows quantitatively the balance between these contributions at the NI phase transition temperature.

cond-mat.soft↗

arXiv2022

Nano-Clustering Mediates Phase Transitions in a Diastereomerically-Stabilized Ferroelectric Nematic System

During the last half-decade, a new class of ferroic-fluid, ferroelectric nematic liquid crystals (NFLCs), creates a noise owing to its exceptional properties such as a colossal polarization, high electro-optic activity plus high fluidity. Regardless of recent huge efforts on design and development of new NFLC molecules based on molecular parameters, the control of NF phase transitions and the stabilization of NF phase are still challenging. Here we discuss the impact of mixing of DIO diastereomer [transDIO (1) and cisDIO (2)] to the NF phase transition, in terms of the smectic cybotactic cluster formation examined by X-ray diffraction. Interestingly, the result suggests that smooth exchange of NFLC 1 by non-LC 2 both with similar dipole and molecular backbone plays a role in the alteration of the NF phase transition.

cond-mat.mtrl-sci↗