P. E. Ramírez-González

arXiv2017

Crossover from Equilibration to Aging: (Non-equilibrium) Theory vs. Simulations

Understanding glasses and the glass transition requires comprehending the nature of the crossover from the ergodic (or equilibrium) regime, in which the stationary properties of the system have no history dependence, to the mysterious glass transition region, where the measured properties are non-stationary and depend on the protocol of preparation. In this work we use non-equilibrium molecular dynamics simulations to test the main features of the crossover predicted by the \emph{molecular} version of the recently-developed multicomponent non-equilibrium self-consistent generalized Langevin equation (NE-SCGLE) theory. According to this theory, the glass transition involves the abrupt passage from the ordinary pattern of full equilibration to the aging scenario characteristic of glass-forming liquids. The same theory explains that this abrupt transition will always be observed as a blurred crossover by the unavoidable finiteness of the time window of any experimental observation. We find that within their finite waiting-time window, the simulations confirm the general trends predicted by the theory.

cond-mat.soft↗

arXiv2007

Simplified Self-Consistent Theory of Colloid Dynamics

One of the main elements of the self-consistent generalized Langevin equation (SCGLE) theory of colloid dynamics [Phys. Rev. E {\bf 62}, 3382 (2000); ibid {\bf 72}, 031107 (2005)] is the introduction of exact short-time moment conditions in its formulation. The need to previously calculate these exact short-time properties constitutes a practical barrier for its application. In this note we report that a simplified version of this theory, in which this short-time information is eliminated, leads to the same results in the intermediate and long-time regimes. Deviations are only observed at short times, and are not qualitatively or quantitatively important. This is illustrated by comparing the two versions of the theory for representative model systems.

cond-mat.mtrl-sci↗