Mode Coupling Relaxation Scenario in a Confined Glass Former

– Molecular dynamics simulations of a Lennard-Jones binary mixture confined in a disordered array of soft spheres are presented. The single particle dynamical behavior of the glass former is examined upon supercooling. Predictions of mode coupling theory are satisfied by the confined liquid. Estimates of the crossover temperature are obtained by power law fit to the diffusion coefficients and relaxation times of the late α region. The b exponent of the von Schweidler law is also evaluated. Similarly to the bulk, different values of the exponent γ are extracted from the power law fit to the diffusion coefficients and relaxation times. The glass transition scenario in confined liquids is a field of rapidly growing interest because of its connection with relevant problems in technology and biology [1]. One of the momentous questions in this field is whether and to what extent theories successfully used for investigating the glass transition in the bulk retain their validity upon confinement. Experiments [2–9] show a rather diversified phenomenology. Although in most cases the process of vitrification of a glass former upon supercooling is not suppressed by confinement, substantial modifications with respect to the bulk behavior are almost always observed In the theoretical framework of the glass transition of bulk liquids a relevant role is played by Mode Coupling Theory (MCT) [10]. This theory is able to predict the approach of the supercooled liquid [11] that is undergoing a calorimetric glass transition to a temperature T C that signals the ideal crossover from a regime where the breaking and the formation of cages is the mechanism that ensures the system to be ergotic to a regime where cages are frozen and only hopping processes restore ergodicity. The approach to the glass transition of binary mixtures in the bulk phase has been the subject of numerous studies, see for example [12–14]. In particular a numerical test of the MCT predictions has been successfully carried out for a Lennard Jones binary mixture (LJBM) [15]. Real porous solids are often disordered, they are made of an interconnected network of voids of various size and shapes. In order to investigate the influence of a disordered microstructure on the glass transition scenario we assume for the solid the same model used in the past both in computer simulation and in statistical mechanical theories to study the modifications of c EDP Sciences