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Workshop on Dispersion Interactions and DFT August 1-3, 2012 Dr. James Parker Program Manager, Molecular Structure and Dynamics Chemical Sciences Division.

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Presentation on theme: "Workshop on Dispersion Interactions and DFT August 1-3, 2012 Dr. James Parker Program Manager, Molecular Structure and Dynamics Chemical Sciences Division."— Presentation transcript:

1 Workshop on Dispersion Interactions and DFT August 1-3, 2012 Dr. James Parker Program Manager, Molecular Structure and Dynamics Chemical Sciences Division U.S. Army Research Office Research Triangle Park, North Carolina

2 Workshop Goal To identify new, innovative methods to include quantitative dispersion interactions (predictive) in DFT calculations without compromising cost or accuracy

3 Molecular Co-Crystal Design Physical and Chemical Properties of Molecular Crystals are Governed by Structure: Polymorphism white, red, and black phosphorus Formwhiteredblack Symmetry bccamorphous ortho- rhombic Reactivity pyro- phoric stable; used in matches low Density Bandgap Ref. Index Properties of Phosphorus

4 Recrystallization (homomeric) or co-crystallization (heteromeric) Recrystallization vs. Co-crystallization Molecular Co-Crystal Design

5 Molecular Co-Crystals  Offers potential to design molecular solid state structures with desired physical and chemical properties  Relies on understanding of molecular interactions in the context of crystal packing Research Barriers  Synthesis: lack of quantitative predictive ability for developing reliable, effective, and versatile synthetic methods (synthons) for the directed assembly of heteromeric co-crystals  Theory: historically, cannot predict accurate crystal structures from a molecular structure.

6 Prismatic habits of TNT:CL-20 co- crystal. Scale bar is 500 μm. Scientific Opportunity: TNT:CL-20 co-crystals are formed in the laboratory  (Matzger) Angew. Chem. 2011, 123,  New energetic co-crystal with 81% energy density of CL-20 with only 66% Cl-20 by mass  Density of co-crystal is 1.91; compare to TNT density of 1.70 and CL-20 density of 2.08  Impact sensitivity of the co-crystal is a factor of 2 less than CL-20 (drop test method)  combines stability of TNT with density and power of CL-20 in one homogeneous material Molecular Co-Crystal Design TNTCL-20 Interactions between TNT and CL-20 in the co-crystal.

7 Scientific Opportunity: New efficient computational chemistry method, SAPT(DFT), can quantitatively predict molecular crystal structures  (Szalewicz) Phys. Chem. Chem. Phys. 2011, 13, The predicted FOX-7 unit cell configuration superimposed onto the experimental structure Molecular Co-Crystal Design a b c Comparison of experimental and predicted crystallographic parameters  Differences are less than 1 percent!

8 Scientific Opportunities  Co-crystal formation of TNT:CL-20 has been directed in the laboratory.  Predictive computational tools are available for molecular crystal design. Impact Areas  molecular crystal properties  novel energetic materials  supramolecular chemistry  crystal engineering  materials science Molecular Co-Crystal Design Intermolecular interactions within the TNT:CL-20 co-crystal


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