Linking transport, structural and relaxation properties of supercooled 1-methylnaphthalene at high pressures via molecular modeling

Journal of Molecular Liquids. 2025. Vol. 440. Article 128894.

Nikitiuk B., Nikolay Kondratyuk, Pisarev V.

Understanding how liquids transition into glassy states under varying thermodynamic conditions remains a fundamental challenge in condensed matter physics. While temperature-driven vitrification has been extensively studied, the effects of high pressure on glass formation are comparatively underexplored -- particularly in molecular liquids. In this work, we employ molecular dynamics simulations to investigate the behaviour of 1-methylnaphthalene under isothermal compression up to 600 MPa at 323 K. Our model displays excellent agreement with experimental data for structural and transport properties at lower pressures. At higher pressures, we identify a dynamic crossover around 350 MPa, where the system enters a supercooled regime. It is evidenced by the breakdown of the Stokes--Einstein relation for translational diffusion, while rotational dynamics continue to obey the Debye--Stokes--Einstein relation. This decoupling reveals the emergence of two distinct dynamic length and time scales for micro- and macro-scale dynamics, further supported by the divergence of various structural relaxation times. Additionally, we identify a sharp crossover in pair entropy scaling of transport coefficients, qualitatively consistent with previously reported effects for excess entropy scaling of model liquids. Therefore, we propose the pair entropy as a computationally effective criterion for supercooling in molecular liquids.

Keywords: relaxation dynamics, Glass Transition, molecular dynamics simulations, Transport properties, pairwise entropy

Publication based on the results of: Advanced materials and technologies (2025)