Seismic anisotropy has been widely observed in crust and mantle materials and plays a key role in the understanding of structure and flow patterns. Although seismic anisotropy can be explained by the crystal preferred orientation (CPO) of highly anisotropic minerals in the crust, that is, amphibole, experimental studies on the CPO of amphibole are limited. Here we present the results of novel experiments on simple shear deformation of amphibolite at high pressure and temperatures (1 GPa, 480–700 °C). Depending on the temperature and stress, the deformed amphibole produced three types of CPOs and resulted in a strong seismic anisotropy. Our data provide a new understanding of the observed seismic anisotropy. The seismic data obtained from the amphibole CPOs revealed that anomalous seismic anisotropy observed in the deep crust, subducting slab and mantle wedge can be attributed to the CPO of amphibole.
Newly discovered 2D Janus transition metal dichalcogenides layers have gained much attention from theory perspective owing to their unique atomic structure and exotic materials properties, but little to no experimental data are available on these materials. Here, our experimental and theoretical studies establish the vibrational and optical behavior of 2D Janus S-W-Se and S-Mo-Se monolayers under high pressures for the first time. CVDgrown classical TMD monolayers were first transferred onto vdW mica substrates and converted to 2D Janus sheets by surface plasma technique, and then integrated into 500µm size diamond anvil cell for high-pressure studies. Our results show that 2D Janus layers do not undergo phase transition up to 15 GPa, and in this pressure regime, their vibrational modes exhibit a non-monotonic response to the applied pressures (d/dP). Interestingly, these 2D Janus monolayers exhibit unique blue-shift in PL upon compression which is in contrast to many other traditional semiconductor materials. Overall theoretical simulations offer in-depth insights and reveal that the overall optical response is a result of competition between the ab-plane (blue-shift) and c-axis (red-shift) compression. Overall findings shed the very first light on how 2D Janus monolayers respond under extreme pressures and expand the fundamental understanding of these materials.Results mark the first high pressure studies on 2D Janus monolayers. Pressure studies show that 2D Janus monolayers S-Mo-Se and S-W-Se do not undergo phase transition up to 15GPa, but their vibrational modes exhibit a non-monotonic response to pressure. Janus S-W-Se monolayer undergo anomalous blue-shifting behavior and direct to indirect bandgap transition.
Properties of liquid silicates under high-pressure and high-temperature conditions are critical for modeling the dynamics and solidification mechanisms of the magma ocean in the early Earth, as well as for constraining entrainment of melts in the mantle and in the present-day core–mantle boundary. Here we present in situ structural measurements by X-ray diffraction of selected amorphous silicates compressed statically in diamond anvil cells (up to 157 GPa at room temperature) or dynamically by laser-generated shock compression (up to 130 GPa and 6,000 K along the MgSiO3glass Hugoniot). The X-ray diffraction patterns of silicate glasses and liquids reveal similar characteristics over a wide pressure and temperature range. Beyond the increase in Si coordination observed at 20 GPa, we find no evidence for major structural changes occurring in the silicate melts studied up to pressures and temperatures exceeding Earth’s core mantle boundary conditions. This result is supported by molecular dynamics calculations. Our findings reinforce the widely used assumption that the silicate glasses studies are appropriate structural analogs for understanding the atomic arrangement of silicate liquids at these high pressures.
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