Institute for Shock Physics

Multi-million atom non-equilibrium molecular dynamics (MD) simulations give significant insight into the transient processes that occur under shock compression. Pico-second X-ray diffraction enables the probing of materials on a timescale fast enough to test such effects. In order to simulate diffraction patterns, Fourier methods are required to gain a picture of reciprocal lattice space. We present here results of fast Fourier transforms of atomic coordinates of shocked crystals simulated by MD, and comment on the computing power required as a function of problem size. The relationship between reciprocal space and particular experimental geometries is discussed.

Diagnostics which probe the lattice response during shock compression offer insight into many fundamental physical phenomena which govern material response. While diffraction from shocked loaded single crystals has been demonstrated for several years the recent development of in-situ polycrystalline diffraction techniques offers similar levels of insight into materials which are more complicated by nature of having grains of multiple orientations, but are more representative of commonly used materials. We will exam both single and polycrystalline iron shock loaded through the α-ɛ transition. This work was conducted under the auspices of the U.S. DOE by the UC LLNL and LANL under Contract No. W-7405-Eng-48. Additional support was provided by LDRD program Project No. 06-SI-004 at LLNL.

Diagnostics which can probe the lattice response during shock compression offer insight into many key features of the physical phenomena which govern material response. An in-depth analysis of diffraction images of the alpha to epsilon transition in shock compressed single crystal iron offers insight into the transition mechanism of the lattice due to compression along the 100 principal axes. These single crystal diffraction techniques integrate well with molecular dynamics simulations, and have been shown to offer insight into the atomistics of the shock process. The recent development of polycrystalline diffraction techniques offers similar levels of insight into materials which are more complicated by their nature of having grains of multiple orientations, but are more representative of commonly used materials. This work was conducted under the auspices of the U.S. DOE by the UC LLNL and LANL under Contract No. W-7405-Eng-48. Additional support was provided by LDRD program Project No. 06-SI-004 at LLNL.

Infectious diseases by multidrug-resistant superbugs, which cannot be cured using commercially available antibiotics, are the biggest threat for our society. Due to the lack of discovery of effective antibiotics in the last two decades, there is an urgent need for the design of new broad-spectrum antisuperbug biomaterials. Herein, we report the development of antisuperbug nanocomposites using human host defense antimicrobial peptide-conjugated biochar. To develop an economically viable technology, biochar, a carbon-rich material from naturally abundant resource, has been used. For combating broad-spectrum superbugs, a nanocomposite has been designed by combining biochar with α-defensin human neutrophil peptide-1 (HNP-1), human β-defensin-1 (hBD-1), and human cathelicidin LL-37 antimicrobial peptide. The designed three-dimensional (3D) nanocomposites with pore size between 200 and 400 nm have been used as channels for water passage and captured superbugs. The reported data demonstrated that antimicrobial nanocomposite can be used for efficient capture and eradication of Gram-negative carbapenem-resistant Enterobacteriaceae (CRE) Escherichia coli (E. coli) and Klebsiella pneumoniae (KPN) superbugs, as well as Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) superbugs. Possible mechanisms for broad-spectrum antisuperbug activities using hydrogel have been discussed.