Properties of energetic materials: United States Department of Energy (DOE) Accelerated Strategic Computing Initiative (ASCI) strategic alliances Page: 4 of 6
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and safety of energetic materials not only requires molecular interaction potentials accurate
at high temperatures and widely varying pressures but also over the wide range of
environments experience by a weapon during its lifetime (e.g. temperatures ranging from -
120F to 120F). Finally, modeling manufacturing processes as well as deriving new,
improved energetic materials requires a fundamental understanding of the structure-
property relationships (nearly synonymous with accurate interaction potentials) of these
materials under processing conditions as well as the performance and safety environments.
Potential-energy surfaces for "generic" crystals have been developed for hydrocarbons and
azabenzenes (e.g., Williams et al., University of Kentucky). Potential energy surfaces for
the most important molecules in high explosives and energetic materials, such as the
nitramines and nitrated/aminated benzenes, may be calculable by extending the same
methods to these molecules. In addition, the calibrations for these potential functions
should be extended beyond ambient conditions to much higher temperatures and pressures
to be relevant to explosive reaction zones.
C. Calculations of physical properties and transport coefficients
Physical properties and transport coefficients must be obtained to advance energetic
material simulations from the molecular scale to larger distance and time scales. Starting
from molecular potential functions it should be possible to provide, essentially from first
principles, many of the required fundamental physical parameters. The physical properties
that must be calculated include density, energy, specific heat, vectoral and scalar
coefficients of thermal and isobaric expansion, elastic constants and derived moduli,
mechanical strength, all as a function of temperature and pressure, for both solids and
liquids. It is also important to develop practical methods to compute stress-strain curves
and transport coefficients such as diffusion, viscosity, and thermal conductivity. These are
harder to obtain due to the more complicated theoretical framework required.
A variety of theoretical tools are required to do these calculations. They include high-level
ab initio quantum electronic structure methods, Monte Carlo methods, and both classical
and quantum mechanical molecular dynamics. Nearly the entire spectrum of modern
computing capabilities must be brought to bear in this work, from high-performance
workstations in stand-alone mode and in clusters, to advanced high-end parallel plaeorms.
D. Simulations of molecular energization mechanisms
Energization mechanisms must be simulated in order to determine the time required for
thermal equilibration among the vibrational, rotational, and translational modes of the
molecules in shocked/strained crystals of energetic material. This problem bears fairly
strongly on questions about the degree to which microscopic (i.e., Angstrom- or
nanometer-scale) initiation must be considered in modeling larger distance/time scale
phenomena in energetic materials.
Some success has been achieved in a related area by Carter White et al. at NRL and Rice et
al. at ARL who have simulated fully developed detonation waves in prototypical systems
such as 2AB -+ A2 + B2 and 2 03 -+ 3 02. In contrast, the aim of this research element is
not to simulate the detonation dynamics, but rather to ferret out the molecular-level details
of the energization process in a shock front and the subsequent energy relaxation that
occurs in the moments subsequent to shock passage but before widespread chemical
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Adams, T.F. Properties of energetic materials: United States Department of Energy (DOE) Accelerated Strategic Computing Initiative (ASCI) strategic alliances, report, January 1, 1997; New Mexico. (digital.library.unt.edu/ark:/67531/metadc680642/m1/4/: accessed November 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.