Articles

August 3, 2012 11:37 AM

Research at the U.S. Department of Energy Office of Science’s Advanced Photon Source (APS) by researchers from Argonne National Laboratory, the Brazilian Synchrotron Light Laboratory, the Carnegie Institution of Washington, and Commissariat à l'énergie atomique-CEA (France) has shown that gaining valence information requires a lot more work when it comes to mixed-valence systems. Their results have been published in the journal Physical Review Letters. (more...)

July 23, 2012 01:15 PM

A Carnegie scientist's observations have led the way to stabilizing tungsten hydrides under high pressure. (more...)

July 2, 2012 04:33 PM

A collaborative experimental effort with Carnegie researchers has discovered unknown properties of a computer memory material that will allow for faster data transfer with a higher capacity of data stored. (more…)(https://www.gl.ciw.edu/news/more_to_store)

June 29, 2012 10:06 AM

The metal-insulator transition at 105Kin the T’-La4Ni3O8 is associated with significant changes of lattice parameters. These changes are consistent with the model of a temperature-driven high-spin to low-spin transition at Tt.  The high pressure structural study at HPCAT reveals that a new T+structure is stabilized under P>21 GPa. The presence of isolated Ni sites with apical oxygen in the T’structure leads to a variable range-hopping conductivity in the low-spin phase in which the transition temperatureis suppressed under pressure. (Cheng et al., Phys. Rev. Lett., 108, 236403, 2012)

February 23, 2012 01:25 PM

In the superconducting iron chalcogenides, a second superconducting phase suddenly reemerges above 11.5 GPa, after the Tc drops from the first maximum of 32K at 1 GPa. The Tc of the re-emerging superconducting phase is higher than the first maximum, reaching 48.0–48.7K for two materials studies. HPCAT experiments show that the basic structure of these compounds was not changed under the extreme pressure and thus further research is needed to determine the origin of the re-appearance at the structural level. The result is published in Nature, Feb. 22, 2012. 
CIW-Geophysical Laboratory
, Advanced Photon Source
(Figure: Pressure dependence of the superconducting temperature)

February 17, 2012 12:57 PM

A miniature X-ray emission spectrometer has been successfully commissioned by a team of researchers from the University of Washington, LLNL and HPCAT. The spectrometer, based on a coarsely diced approximate of the Johansson optics, contains six small flat Ge ( 3 3 1 ) crystals, which are ~7.4cm away from sample and have a total solid angle of ~50msr, roughly equivalent to that of six traditional spherically bent crystal analyzers. The overall energy resolution is ~1.3eV. The new XES spectrometer provides improved efficiency in X-ray emission spectroscopy (XES) measurements, which has been demonstrated in RXES measurements for Pr at high pressures in a diamond anvil cell. (Pacold et. al. J. Synchrotron Rad (2012),  19). (Photograph of the miniXES spectrometer at 16ID-D with DAC and Pilatus in place)

 

February 14, 2012 11:29 AM

White x-ray radiography measurement combined with Paris-Edinburgh cell at the HPCAT beamline 16BM-B provides a capability of investigating viscosity of liquid at high pressure and high temperature conoditions using falling sphere viscometer technique.  A preliminary experiment was carried out for a silicate melt at 3.5 GPa and 1600 °C.  Pt sphere smoothly fell in the silicate melt. Viscosity can be obtained by deriving the falling velocity of the Pt sphere. Video

January 24, 2012 11:31 AM

Sodium displays a great deal of surprising behaviors under high pressure such as melting at room temperature at 118GPa and transition to an insulator over 200GPa. Recent HPCAT experiments measured plasmon excitations of sodium from ambient pressure up to 97GPa using the momentum-dependent inelastic X-ray scattering technique.  The square of zero-momentum plasmon energy increases linearly with densification up to 1.5-fold (~5GPa), which agrees well with a simple free-electron model prediction. From 1.5-fold to 3.7-fold densification at 97GPa, the linear relation curves towards the density axis. However, this deviation can still be explained by a simple metal model. These results showed that even under multiple fold densification the solid Na of both bcc and fcc symmetry can be regarded as simple metals.