Towards a multiscale description of chemistry in shocked materials

There has been much theoretical interest in the microscopic nature of the initiation of widespread chemical reactions in certain materials. Despite concentrated efforts, the mechanisms by which imposed and propagating shocks affect atomistic conditions that favor bond-breaking (thus, chemical reactions) and subsequent macroscopic effects of high pressure in these materials are not fully understood. A theoretical objective, which makes this investigation quite relevant to applied mathematics, is to construct physically reliable multiscale models that encompass nonlinear dynamics, dispersion and chemical transformations in order to predict properties of materials under extreme conditions of pressure. Such models may be used to study stages of evolution of the interior of stars, the aging of energetic materials and other phenomena.

So far, my research in this direction (in collaboration with Efthimios Kaxiras at Harvard and M. Riad Manaa at the Lawrence Livermore National Laboratory) consists of atomistic simulations that aim to capture the combined effect of pressure and molecular vacancies on the atomic structure and electronic properties (such as energy band gaps) of molecular solids. We have focused on the solid nitromethane, a prototypical material (molecular solid), at zero temperature. The longer-term objective is to formulate a macroscopic (continuum) theory that correctly includes the microscopic physics excited by high pressure.

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Related Papers:

1. D. Margetis, E. Kaxiras, M. Elstner, Th. Frauenheim, and M. Riad Manaa, Electronic structure of solid nitromethane: Effects of high pressure and molecular vacancies (PDF), Journal of Chemical Physics, Vol. 117, pp. 788-799 (2002).