Researchers from Lawrence Livermore National Laboratory, University of Nevada Las Vegas, Argonne National Laboratory, and University of Chicago have found a subtle phase transition in 1,3,5-Triamino-2,4,6- trinitrobenzene (TATB). TATB is an important compound in the energetic materials community as it is a highly stable, insensitive explosive. A more complete understanding of this and other energetic materials is crucial for practical use as well as the development of theoretical models. Extensive single-crystal diffraction experiments were carried out at HPCAT—located at the Advanced… more
Congratulations to Professor Yogesh K. Vohra, long time HPCAT user and NNSA-SSAA partner, and team for recognition of their work in part performed at HPCAT. Their article, authored by Samuel L. Moore, Gopi K. Samudrala, Shane A. Catledge, and Yogesh K. Vohra, "… more
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
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