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).