This repository contains experimental data on the thermal conductivity of carbon dioxide (CO2) at high pressures and room temperature. This dataset is presented in a manuscript submitted to Journal of Geophysical Research-Planets by Sean R. Shieh, Wen-Pin Hsieh, Yi-Chih Tsao, Christian Crisostomo, and Han Hsu on January 4, 2022, entitled: Low Thermal Conductivity of Carbon Dioxide at High Pressure: Implications for Icy Planetary Interiors

10.5281/zenodo.6131534

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Structural, spin, and metal-insulator transitions of (Mg,Fe)O at ultrahigh pressure

arXiv (Cornell University) (2020)

Han Hsu Koichiro Umemoto

Fe-bearing MgO [(Mg$_{1-x}$Fe$_x$)O] is considered a major constituent of terrestrial exoplanets. Crystallizing in the B1 structure in the Earth's lower mantle, (Mg$_{1-x}$Fe$_x$)O undergoes a high-spin (HS, $S=2$) to low-spin (LS, $S=0$) transition at $\sim$45 GPa, accompanied by anomalous changes of this mineral's physical properties, while the intermediate-spin (IS, $S=1$) state has not been observed. In this work, we investigate (Mg$_{1-x}$Fe$_x$)O ($x \leq 0.25$) up to $1.8$ TPa via first-principles calculations. Our calculations indicate that (Mg$_{1-x}$Fe$_x$)O undergoes a simultaneous structural and spin transition at $\sim$0.6 TPa, from the B1 phase LS state to the B2 phase IS state, with Fe's total electron spin ($S$) re-emerging from $0$ to $1$ at ultrahigh pressure. Upon further compression, an IS--LS transition occurs in the B2 phase. Depending on the Fe concentration ($x$), metal--insulator transition and rhombohedral distortions can also occur in the B2 phase. These results suggest that Fe and spin transition may affect planetary interiors over a vast pressure range.

Spin transition

Spin states

Metal–insulator transition

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Fault Zone Resistivity Structure and Monitoring at the Taiwan Chelungpu Drilling Project (TCDP)

Terrestrial Atmospheric and Oceanic Sciences (2008)

Chih-Wen Chiang Martyn Unsworth Chow-Son Chen Chien Chih Chen Andrew Tien‐Shun Lin

The Taiwan Chelungpu-fault drilling project (TCDP) has undertaken scientific drilling and directly sampled the sub-surface rupture of the 1999 Chi-Chi earthquake.Audio-magnetotelluric (AMT) measurements were used to investigate electrical resistivity structure at the TCDP site from 2004 -2006.These data show a geoelectric strike direction of N15°E to N30°E.Inversion and forward modeling of the AMT data were used to generate a 1-D resistivity model that has a prominent low resistivity zone (< 10 ohm-m) between depths of 1100 and 1500 m.When combined with porosity measurements, the AMT measurements imply that the ground water has a resistivity of 0.55 ohm-m at the depth of the fault zone.Time variations in the measured AMT data were observed from 2004 -2005 with maximum changes of 43% in apparent resistivity and 18°in phase.The change in apparent resistivity is greatest in the 1000 -100 Hz frequency band.These frequencies are sensitive to the resistivity structure of the upper 500 m of the hanging wall of the Chelungpu Fault.The decrease in resistivity over time appears to be robust and could be caused by an increase in porosity and a re-distribution of the groundwater.

10.3319/tao.2008.19.5.473(t)

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Performance of composite members subjected to axial load and bi-axial bending

Journal of Constructional Steel Research (2008)

Han Hsu F.-J. Jan J.-L. Juang

10.1016/j.jcsr.2008.04.006

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Formation of Iron-Helium Compounds under High Pressure

arXiv (Cornell University) (2024)

Haruki Takezawa Han Hsu Kei Hirose F. Sakai Suyu Fu

While helium is a representative noble gas element characterized by its chemical inertness at ambient conditions, recent experiments and calculations argued that a minor amount of helium is incorporated into molten iron from silicate under high pressures. Here we examined the reaction between iron and helium at 8-42 GPa and ~1000-2820 K and found remarkable volume expansion of the Fe lattice, which is attributed to the formations of fcc and distorted hcp iron-helium compounds with x in FeHex up to 0.13 and 0.42, respectively. Upon releasing pressure under room temperature, these fcc and distorted hcp FeHex were still observed while the former lost some helium. In addition, our first-principles calculations indicate that fcc FeHe0.25, with He atoms in the tetrahedral interstitial sites, is dynamically stable in different magnetic states throughout 0-50 GPa. These results support that the Earth's core can be a large reservoir of primordial 3He.

10.48550/arxiv.2405.11810

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Ferromagnetic insulating state in tensile-strained LaCoO3thin films from LDA+Ucalculations

Physical Review B (2012)

Han Hsu Peter Blaha Renata M. Wentzcovitch

With local density approximation$+$Hubbard $U$ (LDA+$U$) calculations, we show that the ferromagnetic (FM) insulating state observed in tensile-strained LaCoO${}_{3}$ epitaxial thin films is most likely a mixture of low-spin (LS) and high-spin (HS) Co, namely, a HS/LS mixture state. Compared with other FM states, including the intermediate-spin (IS) state (metallic within LDA+$U$), which consists of IS Co only, and the insulating IS/LS mixture state, the HS/LS state is the most favorable one. The FM order in the HS/LS state is stabilized via the superexchange interactions between adjacent LS and HS Co. We also show that the Co spin state can be identified by measuring the electric field gradient at the Co nucleus via nuclear magnetic resonance spectroscopy.

Superexchange

Spin states

Metastability

10.1103/physrevb.85.140404

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Effect of site degeneracies on the spin crossovers in (Mg, Fe)SiO3 perovskite

Physics of The Earth and Planetary Interiors (2009)

Koichiro Umemoto Han Hsu Renata M. Wentzcovitch

Spin Crossover

Spin states

10.1016/j.pepi.2009.10.014

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Citations (30)

Low Thermal Conductivity of Carbon Dioxide at High Pressure: Implications for Icy Planetary Interiors

Journal of Geophysical Research Planets (2022)

S. R. Shieh Wen‐Pin Hsieh Yi‐Chih Tsao Christian P. Crisostomo Han Hsu

Abstract Carbon dioxide is commonly found in terrestrial planets and its thermal property is relevant to the dynamics and evolution of those terrestrial planets. In this work, we combine time‐domain thermoreflectance measurements and first‐principles calculations to determine the thermal conductivity of CO 2 up to 70 GPa at room temperature. Our results show that the thermal conductivity of liquid CO 2 is ∼0.22 W m −1 K −1 at 0.3–0.5 GPa and increases to ∼0.28 W m −1 K −1 when the liquid CO 2 transforms into molecular solid phase I (dry ice). Upon further compression, the mean value of thermal conductivity of phase I increases to 1.4–2.1 W m −1 K −1 at ∼10 GPa and then slightly drops across the phase I‐III boundary. Phase III exhibits a gentle increase of thermal conductivity with pressure and reaches to a maximum value of ∼4 W m −1 K −1 at ∼45 GPa, but shows an abrupt drop when transforming into a non‐molecular amorphous solid. The pressure evolution of CO 2 thermal conductivity across different phases may have significant implications for the heat flow and temperature distribution in the interiors of planets and moons containing CO 2 .

10.1029/2022je007180

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Spin crossover in ferropericlase and its influence on mantle velocities

AGUFM (2010)

Renata M. Wentzcovitch Zhongqing Wu João F. Justo Han Hsu C. R. da Silva

Spin Crossover

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