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Physical Sciences and Mathematics Commons

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Geochemistry

Geoscience Faculty Research

2019

Articles 1 - 2 of 2

Full-Text Articles in Physical Sciences and Mathematics

Chemostratigraphic Correlations Across The First Major Trilobite Extinction And Faunal Turnovers Between Laurentia And South China, Jih-Pai Lin, Frederick A. Sunberg, Ganqing Jiang, Isabel P. Montanez, Thomas Wotte Nov 2019

Chemostratigraphic Correlations Across The First Major Trilobite Extinction And Faunal Turnovers Between Laurentia And South China, Jih-Pai Lin, Frederick A. Sunberg, Ganqing Jiang, Isabel P. Montanez, Thomas Wotte

Geoscience Faculty Research

During Cambrian Stage 4 (~514 Ma) the oceans were widely populated with endemic trilobites and three major faunas can be distinguished: olenellids, redlichiids, and paradoxidids. The lower–middle Cambrian boundary in Laurentia was based on the first major trilobite extinction event that is known as the Olenellid Biomere boundary. However, international correlation across this boundary (the Cambrian Series 2–Series 3 boundary) has been a challenge since the formal proposal of a four-series subdivision of the Cambrian System in 2005. Recently, the base of the international Cambrian Series 3 and of Stage 5 has been named as the base of the Miaolingian …


Pressure-Induced Phase Transition In 1,3,5-Triamino-2,4,6-Trinitrobenzene (Tatb), Brad A. Steele, Samantha M. Clarke, Matthew P. Kroonblawd, I-Feng W. Kuo, Philip F. Pagoria, Sergey N. Tkachev, Jesse S. Smith, Sorin Bastea, Laurence E. Fried, Joseph M. Zaug, Elissaios Stavrou, Oliver Tschauner May 2019

Pressure-Induced Phase Transition In 1,3,5-Triamino-2,4,6-Trinitrobenzene (Tatb), Brad A. Steele, Samantha M. Clarke, Matthew P. Kroonblawd, I-Feng W. Kuo, Philip F. Pagoria, Sergey N. Tkachev, Jesse S. Smith, Sorin Bastea, Laurence E. Fried, Joseph M. Zaug, Elissaios Stavrou, Oliver Tschauner

Geoscience Faculty Research

Determining the unreacted equation of state of 1,3, 5-triamino-2,4,6-trinitrobenzene (TATB) is challenging because it exhibits low crystal symmetry and low X-ray scattering strength. Here, we present the first high-pressure single-crystal X-ray diffraction (SXD) study of this material. Our SXD results reveal a previously unknown transition to a monoclinic phase above 4 GPa. No abrupt change of the volume occurs but the compressibility changes. Concomitant first principles evolutionary crystal structure prediction USPEX calculations confirm this transition and show that it involves a pressure-induced in-plane shift of the layers of TATB molecules with respect to the ambient-pressure phase.