This is a theoretical research grant in which molecular simulations will be used to investigate the effects of stress on disordered systems. The novelty of the research is the use of the energy landscape as a framework for carrying out the simulations and analyzing the results. The use of energy landscapes will lead to new insights regarding these effects and allow long-time phenomena to be addressed.
The investigations will focus on several phenomena involving disordered systems under stress. Specifically, these are (1) the transport properties of flowing fluids; (2) fracture in glassy materials; (3) shock-induced reaction dynamics in energetic materials; (4) amorphous-amorphous phase transitions; and, (5) the effects of stress on aging in glasses. Although these phenomena may appear to be unrelated, this research aims to show that they may be different manifestations of similar stress-induced changes in the underlying energy landscapes.
The following physical picture is proposed to explain the effects of stress on disordered systems: The strains resulting from stress lead to changes in the potential energy landscape - of particular importance are changes in local energy gradients and curvatures, heights of energy barriers, and relative energies of different local energy minima. These changes in the energy landscape alter the system dynamics, which in turn modifies the system properties. Short-time changes in the dynamics, associated with perturbations of the atomic trajectories, are due to changes in local aspects of the energy landscape (e.g., local gradients and curvatures, and barrier heights). Long-time changes of the dynamics, associated with viscoelastic processes, are due to changes in nonlocal aspects of the energy landscape (e.g., relative energies of diffferent regions of the landscape).
The investigation will consist of calculations that map out the effects of strain on the potential energy landscape, along with simulations that probe the system dynamics. These dynamics simulations will include non-equilibrium molecular and Brownian dynamics simulations to address short-time dynamics, and rare-event methods to address long-time dynamics. %%% This is a theoretical research grant in which molecular simulations will be used to investigate the effects of stress on disordered systems. The novelty of the research is the use of the energy landscape as a framework for carrying out the simulations and analyzing the results. The use of energy landscapes will lead to new insights regarding these effects and allow long-time phenomena to be addressed.
The investigations will focus on several phenomena involving disordered systems under stress. Specifically, these are (1) the transport properties of flowing fluids; (2) fracture in glassy materials; (3) shock-induced reaction dynamics in energetic materials; (4) amorphous-amorphous phase transitions; and, (5) the effects of stress on aging in glasses. Although these phenomena may appear to be unrelated, this research aims to show that they may be different manifestations of similar stress-induced changes in the underlying energy landscapes. ***
