Analysis of shear viscosity and viscoelastic relaxation of liquid methanol based on molecular dynamics simulation and mode-coupling theory

Abstract

The role of the prepeak structure of liquid methanol in determining its shear viscosity was studied by means of molecular dynamics (MD) simulation and mode-coupling theory (MCT). The autocorrelation function of the shear stress and the intermediate scattering functions at both the prepeak and the main peak were calculated from the MD trajectories. Their comparison based on MCT suggests that the viscoelastic relaxation in the ps regime is affected by the slow structural dynamics at the prepeak. On the other hand, the MCT for molecular liquids based on the interaction-site model (site-site MCT) fails to describe the coupling between the prepeak dynamics and shear stress. The direct evaluation of the coupling between the two-body density and the shear stress reveals that the viscoelastic relaxation is actually affected by the prepeak dynamics, although the coupling is not captured by the site-site MCT. The site-site MCT works well for a model methanol without partial charges, suggesting that the failure of the site-site MCT originates from the existence of a hydrogen-bonding network structure.

Nanoscopic length scale dependence of hydrogen bonded molecular associates’ dynamics in methanol

“…Further study is required to establish the link between the dynamics observed over different length scales and the macroscopic, specifically rheological, properties of the system. 50…”

Sticky Matters: Jamming and Rigid Cluster Statistics with Attractive Particle Interactions

“…), particles typically attract their neighbors, and pure repulsion can only be realized with careful tuning, if at all. The few existing studies of jamming with attraction reveal significant differences, including a gellike structure with large voids [22,23] and shear banding [24][25][26][27]. Most remarkably, Lois et al [28] showed that strongly attractive soft spheres belong to a new universality class, distinct from both repulsive jamming and rigidity percolation on generic lattices [29,30].…”

“…We adopt the conventions of prior work [23][24][25][26][27][28] and model sticky particles with a repulsive core and attractive shell that experience a central force…”

Multimodal character of shear viscosity response in hydrogen bonded liquids

“…Yet, it is not always obvious how the macroscopic flow is connected to the atomic/molecular dynamics and complex phenomena can emerge from the presence of different kind and degree of intermolecular interactions between molecules, which, in some cases, result in transient network structures and complicate the molecular scale picture of viscosity. Hydrogen bonding and Coulombic interactions for example are responsible for the mesoscopic structure arising in some monoalcohol (MA) and ionic liquids with long alkyl chains [5][6][7][8][9][10][11][12] . The interest in understanding hydrogen bonded networks is ubiquitous while the need to understand the impact of molecular organization on the physicochemical properties of ionic liquids has both a practical and a fundamental basis.…”

“…In essence, molecular arrangement of these liquids in polar and non-polar domains resemble the more long-lived structure of surfactant solutions. Since the characteristic mesoscopic structure of surfactant solutions is responsible for their large structural viscosity, the study of the structure and dynamics of these kind of transient networks and their possible influence in the flowing behaviour of liquids has lately drawn a lot of attention [9][10][11][12][13][14][15][16][17][18][19][20][21] .…”