Nanothermodynamics Applied to Thermal Processes in Heterogeneous Materials

Abstract

Abstract : Small-system thermodynamics provides a novel paradigm for understanding the complex response inside bulk materials. This nanothermodynamics yields a systematic way to treat entropic forces, which come from fluctuations in the density, alignment, and number of interacting particles. Although usually neglected in most computer simulations, these entropic forces can alter reaction rates by several orders of magnitude across length scales of nanometers. We show that such entropic forces are necessary to maintain conservation of energy and maximum entropy during equilibrium fluctuations. Furthermore, adding entropic forces improves agreement between computer simulations and the measured properties of many materials. Another result is that finite-size thermal effects cause simple models to exhibit complex dynamics. To expand the usefulness of our fundamental research, we collaborate with experts in the area of energetic materials. We have found that similar finite-size thermal effects occur in molecular-dynamics simulations of nitromethane. Future applications of nanothermodynamics will be facilitated by continuing to collaborate with such experts. Our goal is to optimize the accuracy, efficiency, and predictive power of large-scale simulations for the complex dynamics inside energetic materials.