A5035775791- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Seismic Performance and Analysis
- Structural Load-Bearing Analysis
- Crystal Structures and Properties
- Structural Behavior of Reinforced Concrete
- Geomagnetism and Paleomagnetism Studies
- Structural Engineering and Vibration Analysis
- Rare-earth and actinide compounds
- Phase Equilibria and Thermodynamics
- Geophysical and Geoelectrical Methods
- Magnetic Properties and Synthesis of Ferrites
- Geological and Geophysical Studies
- earthquake and tectonic studies
- Earthquake Detection and Analysis
- Gas Dynamics and Kinetic Theory
- Graphene research and applications
- Iron oxide chemistry and applications
- Seismic Waves and Analysis
- Hydrocarbon exploration and reservoir analysis
- Structural Analysis and Optimization
- Thermal Expansion and Ionic Conductivity
- Magnetic Properties of Alloys
National Central University
2016-2025
University of Minnesota
2009-2012
University of Minnesota System
2010
Lunghwa University of Science and Technology
2007-2010
The University of Texas at Austin
2005-2007
AbbVie (United States)
2002
Weyl semimetals are novel topological conductors that host fermions as emergent quasiparticles. In this Rapid Communication, we propose a new type of semimetal state breaks both time-reversal symmetry and inversion in the $R\mathrm{AlGe}$ ($R=\mathrm{rare}\ensuremath{-}\mathrm{earth}$) family. Compared to previous predictions magnetic candidates, prediction nodes is more robust less dependent on details magnetism because generated already by breaking ferromagnetism acts simple Zeeman...
Using density functional theory plus Hubbard U calculations, we show that the ground state of (Mg,Fe)(Si,Fe)O(3) perovskite, major mineral phase in Earth's lower mantle, has high-spin ferric iron (S=5/2) at both dodecahedral (A) and octahedral (B) sites. With increasing pressure, B-site undergoes a spin-state crossover to low-spin (S=1/2) between 40 70 GPa, while A-site remains state. This is accompanied by noticeable volume reduction an increase quadrupole splitting, consistent with recent...
We report the formation of fcc and distorted hcp iron-helium compounds with x in FeHex up to 0.13 0.48, respectively, based on experiments at 5–54 GPa ∼1000–2820 K. Upon releasing pressure under room temperature, these were still observed by XRD SIMS measurements. Our first-principles calculations indicate that FeHex, helium atoms occupying tetrahedral trigonal-planar interstitial sites (instead octahedral sites), are dynamically stable throughout 0–50 GPa. These results support Earth's core...
In this paper, we use the local density $\text{approximation}+\text{Hubbard}$ $U$ method to calculate structural and electronic properties of low-spin ${\text{LaCoO}}_{3}$. The Hubbard is obtained by first principles consistent with each fully optimized atomic structure at different pressures. With structurally $U$, agrees experimental data better than calculations fixed or vanishing $U$. A discussion on how affects structures ${\text{LaCoO}}_{3}$ also given.
We demonstrate that the optical absorption of zigzag-edge graphene nanoribbons is qualitatively different from armchair nanotubes. Unlike selection rule for nanotubes, when incident beam polarized along longitudinal direction, interband transitions at direct gaps are forbidden nanoribbons. This due to finite width also edge states play an important role in absorption. They involved many peaks within range $(\ensuremath{\hbar}\ensuremath{\omega}<0.12\phantom{\rule{0.3em}{0ex}}\mathrm{a.u.})$...
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, HS/LS state. Compared with other FM states, including intermediate-spin (IS) (metallic within LDA+$U$), which consists IS Co only, IS/LS state, favorable one. The order stabilized via superexchange interactions between adjacent LS HS...
Abstract We present local density approximation augmented by the Hubbard‐type correction calculations of high‐temperature elastic properties bridgmanite with composition for 0≤×≤0.125. Results moduli and acoustic velocities Mg end‐member ( x =0) agree very well latest high‐pressure experimental measurements. In iron‐bearing system, we focus particularly on change in thermoelastic parameters across state that occurs ferrous iron above ∼30 GPa, often attributed to a high‐spin (HS)...
We study the electronic states and nonlinear motion of $\ensuremath{\pi}$ electrons in an armchair nanotube driven by monochromatic intense laser fields with polarization parallel to axis. The intensity frequency (photon energy) applied are varied so their effect on can be understood. In each case, Floquet-Bloch theory is used calculate states, quasienergy band, mean energy electron current density. By summing up density all occupied harmonic generation spectrum determined. demonstrate that...
Research Article| January 01, 2010 Spin-State Crossover of Iron in Lower-Mantle Minerals: Results DFT+U Investigations Han Hsu; Hsu Department Chemical Engineering and Materials Science, University Minnesota, Minneapolis, Minnesota 55455-0132, U.S.A., hsuhan@cems.umn.edu Search for other works by this author on: GSW Google Scholar Koichiro Umemoto; Umemoto Geology Geophysics, umemoto@cems.umn.edu Zhongqing Wu; Wu Physics, South California, Los Angeles, California 90007, zhongwu@usc.edu...
With a series of local-density approximation plus Hubbard $U$ calculations, we have demonstrated that for lanthanum cobaltite $({\text{LaCoO}}_{3})$, the electric field gradient at cobalt nucleus can be used as fingerprint to identify spin state ion. Therefore, in principle, ion unambiguously determined from nuclear magnetic resonance spectra. Our calculations also suggest crossover low-spin intermediate-spin temperature range 0--90 K is unlikely, based on half-metallic band structure...
Spin crossover of iron is central importance in solid Earth geophysics. It impacts all physical properties minerals that altogether constitute $\ensuremath{\sim}95$ vol% the Earth's lower mantle: ferropericlase [(Mg,Fe)O] and Fe-bearing magnesium silicate $({\mathrm{MgSiO}}_{3})$ perovskite. Despite great strides made past decade, existence an intermediate-spin (IS) state ferrous $({\mathrm{Fe}}^{2+})$ (with total electron spin $S=1)$ its possible role pressure-induced these lower-mantle...
Magnetic properties of fully oxygenated bare CuO nanoparticles have been investigated using magnetization, X-ray diffraction, neutron and Raman scattering measurements. The Langevin field profile is clearly revealed in the isothermal magnetization 8.8 nm nanoparticle assembly even at 300 K, revealing a 172 times enhancement ferromagnetic responses over that bulk CuO. Surface reaches 18% core magnetization. Cu spins order below 400 which 1.7 higher than 231 K observed A relatively simple...
Research Article| August 01, 2009 Magnetotelluric evidence for thick-skinned tectonics in central Taiwan Edward Bertrand; Bertrand 1Department of Physics, University Alberta, Edmonton, Alberta T6G 2R3, Canada Search other works by this author on: GSW Google Scholar Martyn Unsworth; Unsworth Chih-Wen Chiang; Chiang 2Institute Geophysics, National Central University, Chung-Li, Chow-Son Chen; Chen Chien-Chih Francis Wu; Wu 3State New York at Binghamton, 13902-6000, USA Erşan Türkoğlu; Türkoğlu...
Abstract. The Parkinson vectors derived from 3-component geomagnetic data via the magnetic transfer function are discussed with respect to epicentre locations and hypocentre depths of 16 earthquakes (M ≥ 5.5) in Taiwan during a period 2002–2005. To find out whether electric conductivity changes would happen particularly seismoactive depth ranges, i.e. vicinity earthquake foci, frequency dependent penetration electromagnetic waves (skin effect) is taken into account. background distributions...
This study experimentally evaluated the seismic performance of steel knee braced frame structures with energy dissipation mechanism. A series cyclic load tests were conducted on moment resisting frames and proposed frames. Test results validated that demand in beam-to-column connection designs was alleviated by design method. also showed strength stiffness effectively enhanced. Comparisons between further justified applicability
Ferromagnesite, an iron-bearing carbonate stable up to 100--115 GPa, is believed be the major carbon carrier in earth's lower mantle and play a key role deep cycle. In this paper, we use local density approximation plus self-consistent Hubbard $U$ (LDA+${U}_{\mathrm{sc}}$) method study iron spin crossover ferromagnesite with wide range of concentration (12.5--100%). Our calculation shows that mineral undergoes from high-spin (HS) ($S=2$) low-spin (LS) ($S=0$) state at around 45--50...