Calculating Hugoniots for molecular crystals from first principles.
Density Functional Theory (DFT) has over the last few years emerged as an indispensable tool for understanding the behavior of matter under extreme conditions. DFT based molecular dynamics simulations (MD) have for example confirmed experimental findings for shocked deuterium, enabled the first experimental evidence for a triple point in carbon above 850 GPa, and amended experimental data for constructing a global equation of state (EOS) for water, carrying implications for planetary physics. The ability to perform high-fidelity calculations is even more important for cases where experiments are impossible to perform, dangerous, and/or prohibitively expensive. For solid explosives, and other molecular crystals, similar success has been severely hampered by an inability of describing the materials at equilibrium. The binding mechanism of molecular crystals (van der Waals forces) is not well described within traditional DFT. Among widely used exchange-correlation functionals, neither LDA nor PBE balances the strong intra-molecular chemical bonding and the weak inter-molecular attraction, resulting in incorrect equilibrium density, negatively affecting the construction of EOS for undetonated high explosives. We are exploring a way of bypassing this problem by using the new Armiento-Mattsson 2005 (AM05) exchange-correlation functional. The AM05 functional is highly accurate for a wide range of solids, in particular in compression. In addition, AM05 does not include any van der Waals attraction, which can be advantageous compared to other functionals: Correcting for a fictitious van der Waals like attraction with unknown origin can be harder than correcting for a complete absence of all types of van der Waals attraction. We will show examples from other materials systems where van der Waals attraction plays a key role, where this scheme has worked well, and discuss preliminary results for molecular crystals and explosives.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 988556
- Report Number(s):
- SAND2010-1435C; TRN: US201018%%558
- Resource Relation:
- Conference: Proposed for presentation at the 14th International Detonation Symposium held April 11-16, 2010 in Coeur d'Alene, ID.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
BONDING
CARBON
CHEMICAL EXPLOSIVES
COMPRESSION
DENSITY FUNCTIONAL METHOD
DEUTERIUM
EQUATIONS OF STATE
EXPLOSIONS
EXPLOSIVES
CORRELATION FUNCTIONS
FUNCTIONALS
MOLECULAR CRYSTALS
ORIGIN
PHYSICS
TRIPLE POINT
VAN DER WAALS FORCES