at the Advanced Photon Source

Recent HPCAT Science Highlights

The satellite of the 4d3/2 – 2p1/2 emission line (Lγ) has been traditionally interpreted as a signature of the bare (unscreened) magnetic moment of the 4f electrons in the lanthanides [see e.g. B. Maddox et al., PRL 96, 215701 (2006)]. Here, a collaboration of theorists from the University of California at Davis and Stanford along with experimenters from the University of Washington and Lawrence Livermore National Laboratory find that the intensity of the satellite structure of the early light… more

Research led by PhD student Christian Childs from the University of Nevada, Las Vegas, into the transformation of La2Sn2O7 through different extreme conditions pathways has been investigated via the laser-heated diamond anvil cell, X-ray diffraction, Raman spectroscopy, and computational methods. Natural specimens of the pyrochlore (A2Bmore

LLNL and HPCAT scientists recently published an article in RSI describing a high-speed multichannel pyrometer system they developed for measuring the temperature of samples in laser heating experiments.  The system has been used with success at HPCAT.  The team is looking into assembling a system for permanent installation at HPCAT. For more, see Rev. Sci. Instru. 89, 125117 (2018).

Jarosite, KFe3(OH)6(SO4)2, contains perfect 2D kagomé lattices of Fe3+ ions. The geometry of the kagomé lattice engenders magnetic frustration in antiferromagnets, yet jarosite still orders magnetically at 65 K. Given that magnetic frustration can cause exotic emergent phenomena, the magnetism in jarosite has been extensively studied at ambient pressure. Previously, rigorous synthetic magnetostructural substitutional studies varied the interlayer spacing between the kagomé layers. These studies revealed that there is no trend in the Néel temperature in the iron jarosites as a function of… more

When compressed above megabar pressures (>100 GPa), glasses may undergo structural transitions into more densely packed networks that differ from those at ambient pressure. Inelastic x-ray scattering (IXS, or X-ray Raman scattering), which can probe core electron excitation from glasses in a diamond anvil cell (DAC), has enabled exploration of the pressure-induced changes in atomic configurations of elements in oxide glasses under extreme compression. While IXS provides a rare opportunity to probe the pressure-induced bonding transitions, a decade of efforts to collect an IXS signal… more

Recent discoveries of several stable dense hydrous minerals at high pressure–temperature conditions have led to an important implication of a massive water reservoir in the Earth’s lower mantle. A research team used HPCAT facility and demonstrated that (Fe,Al)OOH can be stabilized in a hexagonal lattice at 107–136 GPa and 2,400 K. By combining powder X-ray-diffraction techniques with multigrain indexation, the team has determined this hexagonal hydrous phase with a = 10.5803(6) Å and c = 2.5897(3) Å at 110 GPa, which is stable under the deep lower mantle conditions and can transform to the… more

Topological Kondo insulator possesses characteristics of both the strong electron correlations and the topological configurations, as shown in a mixed-valence material SmB6. YbB6 is a structural analog of SmB6, but remains controversial whether compressed YbB6 material is a topological insulator or a Kondo topological insulator. A research team used HPCAT facility and performed x-ray measurements on YbB6samples. Both the high-pressure powder x-ray diffraction and optical Raman measurements show no trace of structural phase transitions… more

By engineering molecules with mechanically heterogeneous components with a compressible (‘soft’) mechanophore and incompressible (‘hard’) ligands, a research team has created ‘molecular anvils’, resulting in isotropic stress that leads to relative motions of the rigid ligands, anisotropically deforming the compressible mechanophore and activating bonds. Conversely, rigid ligands in steric contact impede relative motion, blocking reactivity. X-ray experiments, including the use of x-ray absorption measurements at HPCAT, demonstrate hydrostatic-pressure-driven redox reactions in metal–… more