| People Highlights |
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CDAC high school intern Maneeshika Madduri was a semifinalist in the 2008 Siemens Competition for Math, Science, and Technology with her project on hydrogen complexation studies in crown ethers. Congratulations!
Steven Jacobsen, CDAC Academic Partner from Northwestern (and former Barbara McClintock Postdoctoral Fellow at the Geophysical Laboratory) has been awarded a Packard Fellowship for Science and Engineering. Jacobsen is among 20 scientists selected nationally this year to receive this grant. The funding will support development of Jacobsen’s nano-pulsed GHz-ultrasonic method to study atomic-scale, physical properties of superhard materials targeted for future technological applications
The Carnegie Institution held its annual Summer Scholars Research Symposium on Wednesday, August 6th. The ten students participating in the program this year presented the results of their work for the entire Broad Branch Road campus community. The presentations covered a wide range of topics, including mineral physics, organic geochemistry, astrobiology, petrology, seismology and astronomy.
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Russell Hemley has been elected Honoris Causa Professor for Energetics, Mechanics, Machinery, and Control Systems of the Russian Academy of Sciences (RAS). The academy is the leading scientific body in Russia. Founded in 1724, it is one of the oldest such organizations in the world. The degree is awarded to the most eminent foreign scientists.
CDAC supports graduate student research and training in the area of high pressure materials science, broadly defined. We accept proposals on a continuing basis from faculty interested in joining the CDAC team as academic partners. Student support consists of salary, tuition/fees and some travel to CDAC facilities for experiments. Please send a one-page statement of research interests and plans to Steve Gramsch, CDAC Coordinator. 
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| Meetings & Symposia |
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Workshop on Advances in High-Pressure Science using Synchrotron X-rays NSLS, Brookhaven National Laboratory Upton, NY October 4, 2008 4th Asian Conference on High Pressure Research 4th AHP Seoul, Korea October 14-17, 2008 More Meetings & Symposia |
| The Surprising Stability of Molecular Nitrogen at High P and T |
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The N-N triple bond in molecular nitrogen is one of the strongest and most stable chemical bonds in nature, giving rise to the two most commonly observed states, the solid and liquid. Molecular nitrogen itself, however, has shown a surprising degree of polymorphism, leading to a complex phase diagram that is still incomplete in the high pressure and temperature regions. Particularly important is the region near the melting line at pressures higher than 50 GPa, where theoretical work and shock wave experiments have suggested the transition to a polymeric form, which occurs at much higher pressures at low temperatures, according to previous static compression experiments.
Recent work by Alexander Goncharov and colleagues at Carnegie and Lawrence Livermore National Laboratory have obtained Raman spectra up to 120 GPa and 2500 K for both solid and fluid nitrogen in an effort to clarify the behavior of this system at high pressures and temperatures. To probe the material directly at high P and T, a pulsed laser to the sample was combined with a second pulsed laser that excited the vibrational spectrum characteristic of the molecular state of the solid. This pulsed Raman spectroscopy technique allows the acquisition of spectra at precisely the peak temperature of the sample, and also reduces the background thermal radiation from a metallic laser light absorber. The spectroscopic data show that nitrogen in the fluid state remains in the molecular form throughout the pressure and temperature ranges investigated, and that there is no evidence to support a fluid-fluid transition. As shown in the figure, the melting line reaches a maximum in temperature with increasing pressure at around 70GPa, followed by a decrease up to a triple point at approximately 87 GPa. This behavior suggests an explanation for the onset of amorphization at still higher pressures and lower temperatures as has been observed previously in SiO2 and H2O [Goncharov, et al., Phys. Rev. Lett., 101, 095502 (2008)]. |
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