A Lighter Filling in Earth’s Core

1. A Lighter Filling in Earth’s Core • The outer core of the Earth, whose composition until now has been a mystery, may consist of an alloy of iron and magnesium. • Researchers in the laboratory created high pressures to make new alloys of iron and magnesium with the same sound propagation properties as the earth’s core. • This is a major step toward predicting earthquakes. • This research will also be significant for high pressure alloy manufacturing techniques. J.-F. Lin et al., Science308, 1892 (24 June 2005) Funded by DOE BES & National Nuclear Security Administration (Carnegie/DOE Alliance Center), NSF, the State of Illinois, and the W. M. Keck Foundation N. Dubrovinskaia et al., Phys. Rev. Lett.95, 245502 (9 December 2005) Funded by DFG, Swedish Research Council (VR), and the Swedish Foundation for Strategic Research (SSF) The Density of States of Iron at high temperatures (red curve) is shifted toward lower energies, indicating a softening of the lattice, which decreases the velocity of compression waves.

2. Studies in Strain Mapping Help Reduce Fatigue in Materials Studies conducted at the ORNL’s High-Temperature Materials Laboratory are helping scientists better understand the overload phenomena during fatigue. The user study was aimed at revealing the mesoscale explain mesoscale? changesthat retard crack growth rate following an overload. which can help in developing micro-mechanical modeling. Computing? Industry/ Manufacturing applications? Industries such as X (Car producers, NASA, semiconductor manufacturers?)are interested in exactly what happens at the molecular scale when materials break. With this information, we could design better materials and predict whether certain materials are sufficient in particular applications. Using neutron diffraction at the HFIR Neutron Residual Stress Mapping Facility, users from the University of Tennessee mapped the elastic/plastic strains in front of the crack tip. Who would be interested in this research? Is other industry participating? Work funded by ???

3. Optimizing Permanent Magnets Permanent magnetic materials play central roles in the conversion of mechanical energy to electricity in alternators, generators and many other products and technologies. Researchers at APS have developed promising ways to enhance magnets, opening new performance possibilities in energy conservation, miniaturization of magnetic devices, and other applications. D. Haskel et al., Phys. Rev. Lett. 95 (21), 217207 (2005). Unit cell of Nd2Fe14B indicating the location of the two unequal Nd crystal sites that are the focus of this study. Funded by DOE

4. Capturing Atomic Processes Preliminary experiments at the SSRL using electron bunches only quadrillionths of a second long have illuminated the motions of atoms, including the atoms of a microchip. These experiments point toward the enormous possibilities opened up in 2008, the start target for the Linac Coherent Light Source, a machine that will generate light so bright and fast that it will: -- Discover and probe new states of matter -- Understand chemical reactions and biological processes in real time -- Image biological materials at the atomic level -- Image chemicals and material structure on the nanoscale Single shot image of x-ray diffracted intensity of an InSb crystal. The ultrafast drop in intensity along the central region of the image results from intense laser induced disordering (i.e. melting). Lindenberg et. al., Science308, 392 (2005). Gaffney et. al., Phys. Rev. Lett., 95, 127501 (2005). Funded by DOE and in collaboration with several universities and national laboratories

5. Water Air (10 Å) Quartz Neutron Reflectivity Reveals Suspected Air Layer under Water Drops on Lily Pads • Dew drops roll off lily pads because their surfaces are hydrophobic (“water fearing”) • An air layer has long-suspected under such a drop • Removal of dissolved gases reduced the layer thickness; aeration increased it • Hydrophobic forces govern protein folding, lipid aggregation, and hence life itself • [Dhaval A. Doshi, Erik B. Watkins, Jaroslaw Majewski, Jacob Israelachvilli, PNAS] Hydrophobic Polymer

6. Neutron protein crystallography solves several complex biological structures. • Data from xylose isomerase recorded 181,797 reflections allowing researchers to map hydrogen. • Xylose isomerase helps convert sucrose to fructose in the body. Bunick and Hanson, ORNL Human insulin data using PCS user-friendly display (left) and a schematic of PCS (below) Protein Crystallography Station, PCS

7. MOF5-4D2 x=0.165 Metal-Organic Frameworks (MOFs): Advanced Storage Materials for the US Hydrogen Economy Future hydrogen and fuel cell technologies depend critically on the discovery of novel materials to store large amounts of hydrogen under ambient conditions. Metal-organic framework (MOF) compounds are nano-porous materials that show promise for hydrogen storage applications because of their tunable pore size and functionality. Neutron powder diffraction and first-principles calculations have allowed researchers to determine the hydrogen adsorption sites and binding energies in MOF5, the most widely studied MOF material. These results not only hold the key to optimizing MOF materials for hydrogen storage applications, but also suggest that MOFs can be used as templates to create artificial interlinked hydrogen nanocages with novel properties. Yildirim and Hartman, Phys. Rev. Lett. 95, 215504 (2006).

8. Rg = 31Å MA explore NC CA New Methods to Determine Complex Structures of Important, Disordered Proteins in, e.g., HIV Recently, scientists at the NIST Center for Neutron Research (NCNR) have developed computer algorithms that can generate and evaluate ensembles of protein structures in solution. The unique aspect of this work is that these calculated structures are subsequently compared to experimental data on real proteins using small-angle neutron scattering techniques to determine which structures match the data. In collaboration with researchers at the National Cancer Institute, the NCNR scientists have applied these new methods to determine the first full-length structures of the human immunodeficiency virus (HIV) coat protein, called “Gag.” Basic Structure of an Immature Retrovirus Particle HIV Gag Protein Structure Modeling (A. Rein et al., J. Mol. Biol. - in preparation.) Calculation Data ~200 Å ~1100 Å Representative Gag Structures 31Å  Rg  38Å Yeager et al., Proc. Nat. Acad. Sciences 95, 7299 (1998).

9. Pinned Layer Depth (nm) Free Layer -1100 G – First Cycle 1050 G – Second Cycle 18 G – First Cycle Neutron Reflectivity Measurements Help to Develop Higher Density Magnetic Storage Devices The discovery of Giant Magnetoresistance (GMR) has led to the rapid development of new, high-density magnetic storage devices. These rely on the phenomenon known as exchange bias, which is not fully understood. A microscopic model of exchange bias may be illuminated by probing the magnetization changes and the field dependent switching of the individual magnetic layers that make up these storage devices. This can be achieved using polarized neutron reflectivity (PNR) measurements, which provide sub-nanometer resolution of the depth-dependent vector magnetization. By collecting PNR data at several points along the hysteresis curve, as shown in the figure at right, one can measure changes in the magnetic properties of the free and pinned magnetic layers in a prototypical computer hard drive read/write head. S. Moyerman et al., J. App. Phys. (2006) In collaboration with San Jose Research Center, Hitachi Global Storage Technologies