APSUO Rosalind Franklin Young Investigator Award
2006 Winner - Wendy L. Mao

The Advanced Photon Source (APS) Users Organization (APSUO) is pleased to announce that Wendy L. Mao is the recipient of the 2006 "Rosalind Franklin Young Investigator Award." The award recognizes important technical or scientific accomplishment by a young investigator that depended on, or is beneficial to, the APS. Dr. Mao received this award on May 3 at the 2006 APS Users Meeting, at which she also presented her work.

Mao has made contributions to an exceptionally broad range of topics, from the structure of graphite under pressure, to the properties of iron-rich materials at the boundary between the Earth's core and mantle, to the synthesis and characterization of a new family of hydrogen storage materials based on molecular compounds.

In her work on graphite, Mao looked at a half-century-old problem of the behavior of graphite when it is compressed at room temperature. It turns, not into diamond, but into an unusual and unexpected phase. The structure and bonding of this phase remained stubbornly enigmatic because existing techniques could not probe electronic structure at high pressure. At the APS, Mao applied x-ray Raman scattering (XRS) spectroscopy to map the detailed changes in the carbon K-edge that give a signature of the bonding. For graphite at high pressure, XRS revealed an unusual bonding arrangement that explained the material's properties. An additional hydrostatic x-ray diffraction study identified its structure. The high photon flux of the APS made the XRS technique feasible in this case. In fact, with this application of XRS, Mao has opened a new fieldinvestigation of the electronic structure of light elements under pressure.

As Mao explains, A big strength of the APS is that there are so many techniques here that can all be applied to the same sample. Our work on graphite under pressure is a good example of an old problem waiting for the right new technique to come along.

Mao later exploited the strange properties of this graphite materialits hardness is both pressure-dependent and reversiblefor experimental hardware that helped her achieve new results at the APS in a different field: studies of deep-Earth minerals. In that work, she discovered an iron-rich silicate that occurs at deep-mantle conditions. The material properties of this new phase may explain the strange seismic features of the D ² zonethe lower 300 kilometers of the mantle, just outside the Earth's molten core. Mao received her bachelor's degree from MIT in 1998 and her Ph.D. from the University of Chicago in 2005. She is currently a J. Robert Oppenheimer Postdoctoral Fellow at Los Alamos National Laboratory. In her current work at Los Alamos, Mao studies the structure of hydrogen clathrates, materials proposed for storing hydrogen for energy applications. Starting from a structure that was stable only at relatively high pressure, she found that with a slight decrease in pressure, the structure transformed into one that then remained stable at ambient pressure and liquid nitrogen temperature. Synchrotron studies helped identify the phase and monitor its stability. This work is also relevant to planetary studies, as such processes might also occur on the gaseous planets.

Selected Publications by Wendy L. Mao (links may require subscription)
Wendy L. Mao et al., Bonding Changes in Compressed Superhard Graphite, Science 302 , 425427 (2003).

Wendy L. Mao et al., Iron-rich silicates in the Earth's D'' layer, Proc. Natl. Acad. Sci. 102 (28), 97519753 (2005).

Wendy L. Mao et al., Hydrogen Clusters in Clathrate Hydrate, Science 297 , 22472249 (2002).