Multidisciplinary Research Program of the University Research Initiative (MURI)

Accurate Theoretical Predictions of the Properties of Energetic Materials

Donald L. Thompson (PI)Department of Chemistry

University of Missouri – Columbia

Motivation

The need for more efficient, faster, and cheaper methods for discovering new energetic materials

The Plan:● Develop theoretical methods that can be used predict the critical properties and behaviors of notional energetic materials● Provide theoretical guidance in the development of new energetic materials

● Better understanding of existing energetic materials● Advances in theoretical & computational methods

OVERARCHING GOALSPredictive capabilities for energetic materials applicable to the chemical decomposition of condensed-phase energetic materials under extreme conditions to enhance our understanding of current materials and aid in the design and discovery of new ones.

A practical method for predicting solvation and separation in supercritical fluids.

Specific Goals• Potentials that describe the inter- and intra-molecular forces, including phase transitions and chemical reactions.

• Ab initio predictions of structures and properties of solids at high temperatures and pressures.

• Methods to predict mechanical properties and physical changes in condensed phases.

• Methods to predict chemical decomposition in condensed phases, particularly ignition and sensitivity in response to heating and shocking.

• Methods for predicting temperatures of the condensed phases and flames resulting from physical and chemical changes, including a predictive model for the “heat feedback” from the flame to burning surface.

• Methods for predicting solvation and separation for energetic materials in supercritical fluids.

Advances in basic theoretical methods

• Advanced methods for ab initio treatments of condensed phase materials, including chemical changes

• Advanced methods for ab initio predictions of reaction energetics

• New methods for using ab initio quantum chemistry methods in conjunction with molecular dynamics methods

• General universal atomic-level potentials for describing complex chemical reaction, particularly for combustion of C,N,O,H systems.

• Accurate methods for predicting molecular solubility

• Improved practical methods for computing rates

• Improved methods for performing atomic-level simulations

• Methods for realistic simulations of chemistry in condensed phases

• A better understanding of gas-liquid energy transfer

• Others…

Transitioning the Methods

There are ongoing interactions with and feedback from the Army for the immediate transitioning of methods and results for DoD applications

We are working closely with Dr. Betsy Rice to immediately hand off new developments: The models and methods are being continuously tested and incorporated into Army modeling codes.

The Expertise

The MURI brings together the requisite expertise to develop

the theory, models, computational methods, and computer

codes for accurate predictions of the properties and behaviors

of energetic materials.

The MURI TeamJohn E. Adams (University of Missouri, Columbia)

Flame-Surface Heat ExchangeHerman L. Ammon (University of Maryland)

Crystal ModelsRodney J. Bartlett (University of Florida)

Ab Initio Potential Energy Surfaces Donald W. Brenner (North Carolina State University)

Reactive Potentials David M. Ceperley and Richard M. Martin (University of Illinois, Urbana-Champaign)

Quantum Simulations of Materials Donald L. Thompson (University of Missouri, Columbia)

Simulations and Rates Christopher J. Cramer and Donald G. Truhlar (University of Minnesota)

Separation and Solvation

David M. Ceperley and Richard M. MartinUniversity of Illinois, Urbana-Champaign

Development of Fundamental Methods for Prediction of Properties of Materials Under Extreme Conditions

Develop methods for first-principles simulations

Provide benchmarks that can be used in constructing universal force field models

Rodney J. BartlettUniversity of Florida

Ab Initio Predictions for Potential Energy Surfaces

for Chemical Reactions

Develop better Q.M. methods for computing

accurate PESs

Provide critical data for the classical potentials

Develop methods for direct dynamics

Herman L. AmmonUniversity of Maryland

Structure-Density-Heat of Formation-Sensitivity Predictions

Develop procedures for predictions of crystal structures, densities and heats of formation of energetic materials

Investigate the relationships between crystal structure/microstructure and sensitivity, compressibility, polymorphism and crystal shape

Test procedures by predictions for known energetic materials

Donald W. BrennerNorth Carolina State University

Quantum-Based, Reactive Potentials for Simulating Shock Dynamics of Condensed-Phase Energetic Materials:A Bridge between Ab Initio Calculations and Experimental Shock Dynamics

Developing a transferable analytic reactive potential for C,H,O,N species, e.g., RDX & HMX, based on a bond-order formalism and ab initio data that will enable large-scale, 3-D MD simulations Validating specific reaction paths and rates Will predict system properties related to shock initiation and detonation for a wide range of energetic materials Bridge molecular ab initio studies and the macroscale properties of shocked, condensed-phase energetic materials Validation of the potentials across length scales Initial focus: Hydrazine, RDX and HMX.

John E. AdamsUniversity of Missouri, Columbia

Gas-Liquid Interactions: Flame-Surface Heat Exchange

Develop accurate models to aid in the prediction of the burning rate of solid-phase energetic materials

Predictions of the temperature of the fluid layer that forms between the flame and the underlying solid surface

Develop quantitative model for the energy feedback from flame to surface.

Link the MURI condensed-phase models with the steady-state continuum model of Miller and Anderson

Christopher J. Cramer and Donald G. Truhlar

University of Minnesota Prediction of Separation and Solvation Behavior

Develop models for computing free energies of transfer of molecules between the gas phase, the liquid phase, and the solid phase, and into supercritical fluids. Base models on both semiempirical and first-principles methods

Achieve a better understanding of the solubility and other properties of substances in supercritical fluids

Employ that understanding to develop supercritical fluid technologies for recycling and reclamation of energetic materials