Glassy dynamics in a confined monatomic fluid

Abstract

Molecular dynamic simulations of a strongly inhomogeneous system reveals that a single-component soft-sphere fluid can behave as a fragile glass former due to confinement. The self-intermediate scattering function, F(s)(k,t), of a Lennard-Jones fluid confined in slit-shaped pores, which can accommodate two to four fluid layers, exhibits a two-step relaxation at moderate temperatures. The mean-squared displacement data are found to follow time-temperature superposition and both the self-diffusivity and late α relaxation times exhibit power-law divergences as the fluid is cooled. The system possesses a crossover temperature and follows the scalings of mode coupling theory for the glass transition. The temperature dependence of the self-diffusivity can be expressed using the Vogel-Fulcher-Tammann equation, and estimates of the fragility index of the system indicates a fragile glass former. At lower temperatures, signatures of additional relaxation processes are observed in the various dynamical quantities with a three-step relaxation observed in the F(s)(k,t).

Tagged-particle motion in a dense confined liquid

“…In contrast, external walls can be utilized to squeeze dense liquids into narrow pores, channels or wedges. A multitude of simulations and experiments address the question of how confinement affects the dynamics of dense liquids for various particle-wall interactions or roughness of the walls [21][22][23][24][25][26][27][28][29][30][31]. Relaxation times or transport coefficients such as the diffusion coefficient are then suitable measures to characterize the rapidity of particle motion.…”

Structural quantities of quasi-two-dimensional fluids

“…Refs. [5,[10][11][12][13] and references therein) as well as their dynamic properties [14][15][16][17][18][19][20]. The simplest realization of confinement consists of enclosing the fluid in a slit geometry between two parallel walls.…”

Multiple reentrant glass transitions in confined hard-sphere glasses

“…Reentrant scenarios have been uncovered, for example, upon adding a short-range attraction to colloidal particles [6][7][8], by competing near ordering in binary mixtures [9,10], or by inserting the liquid in a frozen disordered host structure [11][12][13]. However, instead of changing the structure of the liquid directly, one may also affect its properties by purely geometric means, via an increase of its confinement [14][15][16][17][18][19][20][21][22][23][24]. Depending on the ratio of the characteristic confinement length (e.g., the wall separation) to particle diameter, this can either lead to an increase or decrease of the first peak of the pair distribution function-the latter being a measure of the "stiffness" of the local packing structure [18].…”