1,143 results on '"Ho-Kwang Mao"'
Search Results
2. Pressure stabilizes ferrous iron in bridgmanite under hydrous deep lower mantle conditions
- Author
-
Li Zhang, Yongjin Chen, Ziqiang Yang, Lu Liu, Yanping Yang, Philip Dalladay-Simpson, Junyue Wang, and Ho-kwang Mao
- Subjects
Science - Abstract
Abstract Earth’s lower mantle is a potential water reservoir. The physical and chemical properties of the region are in part controlled by the Fe3+/ΣFe ratio and total iron content in bridgmanite. However, the water effect on the chemistry of bridgmanite remains unclear. We carry out laser-heated diamond anvil cell experiments under hydrous conditions and observe dominant Fe2+ in bridgmanite (Mg, Fe)SiO3 above 105 GPa under the normal geotherm conditions corresponding to depth > 2300 km, whereas Fe3+-rich bridgmanite is obtained at lower pressures. We further observe FeO in coexistence with hydrous NiAs-type SiO2 under similar conditions, indicating that the stability of ferrous iron is a combined result of H2O effect and high pressure. The stability of ferrous iron in bridgmanite under hydrous conditions would provide an explanation for the nature of the low-shear-velocity anomalies in the deep lower mantle. In addition, entrainment from a hydrous dense layer may influence mantle plume dynamics and contribute to variations in the redox conditions of the mantle.
- Published
- 2024
- Full Text
- View/download PDF
3. A novel method for determining the resistivity of compressed superconducting materials
- Author
-
Liling Sun, Qi Wu, Shu Cai, Yang Ding, and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
The measurement of resistivity in a compressed material within a diamond anvil cell presents significant challenges. The high-pressure experimental setup makes it difficult to directly measure the size changes induced by pressure in the three crystallographic directions of the sample. In this study, we introduce a novel and effective method that addresses these technical challenges. This method is anticipated to offer a valuable foundation for high-pressure investigations on quantum materials, particularly those with anisotropic layered structures.
- Published
- 2024
- Full Text
- View/download PDF
4. Electride Formation of HCP‐Iron at High Pressure: Unraveling the Origin of the Superionic State of Iron‐Rich Compounds in Rocky Planets
- Author
-
Ina Park, Yu He, Ho‐kwang Mao, Ji Hoon Shim, and Duck Young Kim
- Subjects
Earth's inner core ,electride ,hcp iron ,iron hydride ,superionicity ,Science - Abstract
Abstract Electride possesses electrons localized at interstitial sites without attracting nuclei. It brings outstanding material properties not only originating from its own loosely bounded characteristics but also serving as a quasiatom, which even chemically interacts with other elemental ions. In elemental metals, electride transitions have been reported in alkali metals where valence electrons can easily gain enough kinetic energy to escape nuclei. However, there are few studies on transition metals. Especially iron, the key element of human technology and geophysics, has not been studied in respect of electride formation. In this study, it is demonstrated that electride formation drives the superionic state in iron hydride under high‐pressure conditions of the earth's inner core. The electride stabilizes the iron lattice and provides a pathway for hydrogen diffusion by severing the direct interaction between the metal and the volatile element. The coupling between lattice stability and superionicity is triggered near 100 GPa and enhanced at higher pressures. It is shown that the electride‐driven superionicity can also be generalized for metal electrides and other rocky planetary cores by providing a fundamental interaction between the electride of the parent metal and doped light elements.
- Published
- 2024
- Full Text
- View/download PDF
5. Unveiling a novel metal-to-metal transition in LuH2: Critically challenging superconductivity claims in lutetium hydrides
- Author
-
Dong Wang, Ningning Wang, Caoshun Zhang, Chunsheng Xia, Weicheng Guo, Xia Yin, Kejun Bu, Takeshi Nakagawa, Jianbo Zhang, Federico Gorelli, Philip Dalladay-Simpson, Thomas Meier, Xujie Lü, Liling Sun, Jinguang Cheng, Qiaoshi Zeng, Yang Ding, and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Following the recent report by Dasenbrock-Gammon et al. [Nature 615, 244–250 (2023)] of near-ambient superconductivity in nitrogen-doped lutetium trihydride (LuH3−δNε), significant debate has emerged surrounding the composition and interpretation of the observed sharp resistance drop. Here, we meticulously revisit these claims through comprehensive characterization and investigations. We definitively identify the reported material as lutetium dihydride (LuH2), resolving the ambiguity surrounding its composition. Under similar conditions (270–295 K and 1–2 GPa), we replicate the reported sharp decrease in electrical resistance with a 30% success rate, aligning with the observations by Dasenbrock-Gammon et al. However, our extensive investigations reveal this phenomenon to be a novel pressure-induced metal-to-metal transition intrinsic to LuH2, distinct from superconductivity. Intriguingly, nitrogen doping exerts minimal impact on this transition. Our work not only elucidates the fundamental properties of LuH2 and LuH3, but also critically challenges the notion of superconductivity in these lutetium hydride systems. These findings pave the way for future research on lutetium hydride systems, while emphasizing the crucial importance of rigorous verification in claims of ambient-temperature superconductivity.
- Published
- 2024
- Full Text
- View/download PDF
6. Measurement of ferric iron in Chang’e-5 impact glass beads
- Author
-
Lixin Gu, Yangting Lin, Yongjin Chen, Yuchen Xu, Xu Tang, Sen Hu, Ho-kwang Mao, and Jinhua Li
- Subjects
Lunar soils ,Chang’e-5 ,Ferric iron ,EELS ,Beam damage ,Geography. Anthropology. Recreation ,Geodesy ,QB275-343 ,Geology ,QE1-996.5 - Abstract
Abstract The lunar surface and interior are highly reducing, resulting in the virtually absence of ferric ion. However, recent studies suggest the presence of ferric iron in lunar samples, and in most cases they were found in amorphous silicates (e.g., glass beads) measured by TEM–EELS. In this work, we conducted a systematic TEM–EELS analysis on the iron valence states of Chang’e-5 impact glass beads. The Fe3+/ΣFe ratio of each silicate glass sample was determined from integral intensity of Fe L3 and L2 edge. The measurements show a positive correlation between the dwell time and Fe3+/ΣFe ratio, which reveals that ferric iron can be significantly produced by electron beam bombardment under routine analytical condition. The calculated Fe3+/ΣFe with short dwell times (≤ 20 ms) in our Chang’e-5 impact glass beads show no detectable inherent ferric iron, suggesting that the ferric iron is not ubiquitous as previously reported. It is obvious that a careful control of experiment conditions is critical to determine the inherent redox state of other beam-sensitive terrestrial and extraterrestrial samples. Graphical Abstract
- Published
- 2023
- Full Text
- View/download PDF
7. Temperature Dependence of H2O Solubility in Al‐Free Stishovite
- Author
-
Narangoo Purevjav, Hongzhan Fei, Takayuki Ishii, Giacomo Criniti, Yanhao Lin, Ho‐Kwang Mao, and Tomoo Katsura
- Subjects
water solubility in stishovite ,water in deep mantle ,subducting slabs ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Abstract The role of stishovite in transporting water in subducting slabs has been a subject of debate for several decades. Here we investigated stishovite's water solubility and its potential role in water transportation as a function of temperature from 1300 to 2100°C at 22 GPa. Under water‐saturated conditions, high‐quality, Al‐free stishovite single crystals were synthesized with multi‐anvil press, and their water contents were measured using infrared spectroscopy. The H2O solubility in stishovite increases from 128(20) to 521(47) wt. ppm with increasing temperature from 1300 to 1700°C and decreased to 145(26) wt. ppm at 2100°C. The maximum H2O content was about seven times larger than earlier high‐temperature multi‐anvil studies but significantly lower than recent laser‐heated diamond anvil cell and low‐temperature multi‐anvil studies. We suggest that Al‐free stishovite may not be a significant H2O carrier in subducting slabs, at least at the topmost lower mantle corresponding to our experimental conditions.
- Published
- 2024
- Full Text
- View/download PDF
8. 2022 HP special volume: Interdisciplinary high pressure science and technology
- Author
-
Ho-Kwang Mao, Bin Chen, Huiyang Gou, Kuo Li, Jin Liu, Lin Wang, Hong Xiao, and Wenge Yang
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Published
- 2023
- Full Text
- View/download PDF
9. Superionic effect and anisotropic texture in Earth’s inner core driven by geomagnetic field
- Author
-
Shichuan Sun, Yu He, Junyi Yang, Yufeng Lin, Jinfeng Li, Duck Young Kim, Heping Li, and Ho-kwang Mao
- Subjects
Science - Abstract
Earth’s inner core is heterogeneous and anisotropic. A new study based on computational simulation reveals the presence of ionic hydrogen flux in iron crystals, driven by the dipole geomagnetic field, which promotes the formation of observed inner core structure.
- Published
- 2023
- Full Text
- View/download PDF
10. Triggering dynamics of acetylene topochemical polymerization
- Author
-
Xingyu Tang, Xiao Dong, Chunfang Zhang, Kuo Li, Haiyan Zheng, and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Topochemical reactions are a promising method to obtain crystalline polymeric materials with distance-determined regio- or stereoselectivity. It has been concluded on an empirical basis that the closest intermolecular C⋯C distance in crystals of alkynes, d(C⋯C)min, should reach a threshold of ∼3 Å for bonding to occur at room temperature. To understand this empirical threshold, we study here the polymerization of acetylene in the crystalline state under high pressure by calculating the structural geometry, vibrational modes, and reaction profile. We find d(C⋯C)min to be the sum of an intrinsic threshold of 2.3 Å and a thermal displacement of 0.8 Å (at room temperature). Molecules at the empirical threshold move via several phonon modes to reach the intrinsic threshold, at which the intermolecular electronic interaction is sharply enhanced and bonding commences. A distance–vibration-based reaction picture is thus demonstrated, which provides a basis for the prediction and design of topochemical reactions, as well as an enhanced understanding of the bonding process in solids.
- Published
- 2023
- Full Text
- View/download PDF
11. Discovery of the Baijifeng impact structure in Tonghua, Jilin, China
- Author
-
Ming Chen, Yang Lu, Jiahao Ning, Wenge Yang, Jinfu Shu, and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
An impact structure 1400 m in diameter, formed by a bolide impact, has been discovered on Baijifeng Mountain in Tonghua City in Northeast China’s Jilin province. The impact structure takes the form of a cirque-shaped depression on the top of the mountain and is located in a basement mainly composed of Proterozoic sandstone and Jurassic granite. A large number of rock fragments composed mainly of sandstone, with a small amount of granite, are distributed on the top of Baijifeng Mountain. Planar deformation features (PDFs) have been found in quartz in the rock and mineral clasts collected from the surface inside the depression. The forms of the PDFs indexed in the quartz include among others, {101̄3}, {101̄2}, and {101̄1}. The presence of these PDFs provides diagnostic evidence for shock metamorphism and the impact origin of the structure. The impact event took place after the Jurassic Period and probably much later.
- Published
- 2023
- Full Text
- View/download PDF
12. The near-room-temperature upsurge of electrical resistivity in Lu-H-N is not superconductivity, but a metal-to-poor-conductor transition
- Author
-
Di Peng, Qiaoshi Zeng, Fujun Lan, Zhenfang Xing, Yang Ding, and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
The recent report of superconductivity in nitrogen-doped lutetium hydride (Lu-H-N) at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors. However, the failure of scientists worldwide to independently reproduce these results has cast intense skepticism on this exciting claim. In this work, using a reliable experimental protocol, we synthesized Lu-H-N while minimizing extrinsic influences and reproduced the sudden change in resistance near room temperature. With quantitative comparison of the temperature-dependent resistance between Lu-H-N and the pure lutetium before reaction, we were able to clarify that the drastic resistance change is most likely caused by a metal-to-poor-conductor transition rather than by superconductivity. Herein, we also briefly discuss other issues recently raised in relation to the Lu-H-N system.
- Published
- 2023
- Full Text
- View/download PDF
13. No evidence of superconductivity in a compressed sample prepared from lutetium foil and H2/N2 gas mixture
- Author
-
Shu Cai, Jing Guo, Haiyun Shu, Liuxiang Yang, Pengyu Wang, Yazhou Zhou, Jinyu Zhao, Jinyu Han, Qi Wu, Wenge Yang, Tao Xiang, Ho-kwang Mao, and Liling Sun
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
A material described as lutetium–hydrogen–nitrogen (Lu-H-N in short) was recently claimed to have “near-ambient superconductivity” [Dasenbrock-Gammon et al., Nature 615, 244–250 (2023)]. If this result could be reproduced by other teams, it would be a major scientific breakthrough. Here, we report our results of transport and structure measurements on a material prepared using the same method as reported by Dasenbrock-Gammon et al. Our x-ray diffraction measurements indicate that the obtained sample contains three substances: the face-centered-cubic (FCC)-1 phase (Fm-3m) with lattice parameter a = 5.03 Å, the FCC-2 phase (Fm-3m) with a lattice parameter a = 4.755 Å, and Lu metal. The two FCC phases are identical to the those reported in the so-called near-ambient superconductor. However, we find from our resistance measurements in the temperature range from 300 K down to 4 K and the pressure range 0.9–3.4 GPa and our magnetic susceptibility measurements in the pressure range 0.8–3.3 GPa and the temperature range down to 100 K that the samples show no evidence of superconductivity. We also use a laser heating technique to heat a sample to 1800 °C and find no superconductivity in the produced dark blue material below 6.5 GPa. In addition, both samples remain dark blue in color in the pressure range investigated.
- Published
- 2023
- Full Text
- View/download PDF
14. Nested order-disorder framework containing a crystalline matrix with self-filled amorphous-like innards
- Author
-
Kejun Bu, Qingyang Hu, Xiaohuan Qi, Dong Wang, Songhao Guo, Hui Luo, Tianquan Lin, Xiaofeng Guo, Qiaoshi Zeng, Yang Ding, Fuqiang Huang, Wenge Yang, Ho-Kwang Mao, and Xujie Lü
- Subjects
Science - Abstract
The synthesis and characterization of new crystalline-amorphous hybrid materials is challenging. Here, the authors report the preparation of a nested order-disorder framework by applying high pressure to a nested copper chalcogenide Cu12Sb4S13.
- Published
- 2022
- Full Text
- View/download PDF
15. Dense hydrous silica carrying water to the deep Earth and promotion of oxygen fugacity heterogeneity
- Author
-
Yanhao Lin and Ho-Kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Water has remarkable effects on the properties of mantle rocks, but, owing to the high temperatures in the mantle, uncertainties remain about how and how much water is transported into the deep Earth. Recent studies have shown that stishovite and post-stishovites as high-pressure phases of SiO2 have the potential to carry weight percent levels of water into the Earth’s interior along the geotherm of the subducting oceanic crust. As slabs are subducted to the deepest mantle, dehydration of these dense hydrous silica phases has the potential to change the physicochemical properties of the mantle by reducing melting points, forming new high-pressure phases, and enhancing the oxygen fugacity heterogeneity of the lower mantle.
- Published
- 2022
- Full Text
- View/download PDF
16. Geomimicry—Liberating high-pressure research by encapsulation
- Author
-
Ho-Kwang Mao and Wendy L. Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
High pressures induce changes of properties and structures that could greatly impact materials science if such changes were preserved for ambient applications. Mimicking the geological process of diamond formation that the pressures and high-pressure phases in diamond inclusions can be preserved by the strong diamond envelope, we discuss the perspectives that such process revolutionizes high-pressure science and technology and opens a great potential for creation of functional materials with extremely favorable properties.
- Published
- 2022
- Full Text
- View/download PDF
17. Hydrogen and related matter in the pressure dimension
- Author
-
Ho-Kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Published
- 2022
- Full Text
- View/download PDF
18. Chemical transformations of n-hexane and cyclohexane under the upper mantle conditions
- Author
-
Xin Yang, Yapei Li, Yajie Wang, Haiyan Zheng, Kuo Li, and Ho-kwang Mao
- Subjects
Alkanes ,High pressure and high temperature ,Dehydrogenation ,Hydrocarbon ,Upper mantle conditions ,Geology ,QE1-996.5 - Abstract
Alkanes are an important part of petroleum, the stability of alkanes under extreme conditions is of great significance to explore the origin of petroleum and the carbon cycle in the deep Earth. Here, we performed Raman and infrared (IR) spectroscopy studies of n-hexane and cyclohexane under high pressure up to ~42 GPa at room temperature (RT) and high temperature (HT). n-Hexane and cyclohexane undergo several phase transitions at RT around 1.8, 8.5, 18 GPa and 1.1, 2.1, 4.6, 13, 30 GPa, respectively, without any chemical reaction. By using resistive heating combined with diamond anvil cell at pressure up to 20 GPa and temperature up to 1000 K, both n-hexane and cyclohexane decompose to hydrogenated graphitic carbon and n-hexane exhibits higher stability than cyclohexane. Our results indicate that hydrocarbons tend to dehydrogenate in the upper mantle, and the extension of carbon chains may lead to the formation of some unsaturated compounds and eventually transfer into graphitic products.
- Published
- 2021
- Full Text
- View/download PDF
19. The stability of subducted glaucophane with the Earth’s secular cooling
- Author
-
Yoonah Bang, Huijeong Hwang, Taehyun Kim, Hyunchae Cynn, Yong Park, Haemyeong Jung, Changyong Park, Dmitry Popov, Vitali B. Prakapenka, Lin Wang, Hanns-Peter Liermann, Tetsuo Irifune, Ho-Kwang Mao, and Yongjae Lee
- Subjects
Science - Abstract
Along the cold subduction geotherm, glaucophane remains stable down to pressure and temperature (P–T) conditions of ca. 240 km depth, whereas under the warm subduction geotherm, it dehydrates and breaks down into pyroxenes and silica between ca. 50 and 100 km depths.
- Published
- 2021
- Full Text
- View/download PDF
20. Pressure-stabilized divalent ozonide CaO3 and its impact on Earth’s oxygen cycles
- Author
-
Yanchao Wang, Meiling Xu, Liuxiang Yang, Bingmin Yan, Qin Qin, Xuecheng Shao, Yunwei Zhang, Dajian Huang, Xiaohuan Lin, Jian Lv, Dongzhou Zhang, Huiyang Gou, Ho-kwang Mao, Changfeng Chen, and Yanming Ma
- Subjects
Science - Abstract
Calcium and oxygen are abundant elements in the Earth’s mantle, largely present as calcium oxide. Here the authors show, by experiments and computations, that calcium ozonide (CaO3) is stabilized at the high pressures and temperatures characteristic of the lower mantle, with implications for the deep Earth’s chemistry.
- Published
- 2020
- Full Text
- View/download PDF
21. Role of hydrogen and proton transportation in Earth’s deep mantle
- Author
-
Qingyang Hu and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Hydrogen (H) is the most abundant element in the known universe, and on the Earth’s surface it bonds with oxygen to form water, which is a distinguishing feature of this planet. In the Earth’s deep mantle, H is stored hydroxyl (OH−) in hydrous or nominally anhydrous minerals. Despite its ubiquity on the surface, the abundance of H in the Earth’s deep interior is uncertain. Estimates of the total H budget in the Earth’s interior have ranged from less than one hydrosphere, which assumes an H-depleted interior, to hundreds of hydrospheres, which assumes that H is siderophile (iron-loving) in the core. This discrepancy raises the questions of how H is stored and transported in the Earth’s deep interior, the answers to which will constrain its behavior in the deep lower mantle, which is defined as the layer between 1700 km depth and the core–mantle boundary.
- Published
- 2021
- Full Text
- View/download PDF
22. Born’s valence force-field model for diamond at terapascals: Validity and implications for the primary pressure scale
- Author
-
Qingyang Hu and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Born’s valence force-field model (VFM) established a theoretical scheme for calculating the elasticity, zero-point optical mode, and lattice dynamics of diamond and diamond-structured solids. In particular, the model enabled the derivation of a numerical relation between the elastic moduli and the Raman-active F2g mode for diamond. Here, we establish a relation between the diamond Raman frequency ω and the bulk modulus K through first-principles calculation, rather than extrapolation. The calculated K exhibits a combined uncertainty of less than 5.4% compared with the results obtained from the analytical equation of the VFM. The results not only validate Born’s classic model but also provide a robust K–ω functional relation extending to megabar pressures, which we use to construct a primary pressure scale through Raman spectroscopy and the crystal structure of diamond. Our computations also suggest that currently used pressure gauges may seriously overestimate pressures in the multi-megabar regime. A revised primary scale is urgently needed for such ultrahigh pressure experiments, with possible implications for hot superconductors, ultra-dense hydrogen, and the structure of the Earth’s core.
- Published
- 2021
- Full Text
- View/download PDF
23. Coupled deep-mantle carbon-water cycle: Evidence from lower-mantle diamonds
- Author
-
Wenzhong Wang, Oliver Tschauner, Shichun Huang, Zhongqing Wu, Yufei Meng, Hans Bechtel, and Ho-Kwang Mao
- Subjects
diamond ,deep mantle ,water and carbon cycle ,first-principles calculations ,Science (General) ,Q1-390 - Abstract
Diamonds form in a variety of environments between subducted crust, lithospheric and deep mantle. Recently, deep source diamonds with inclusions of the high-pressure H2O-phase ice-VII were discovered. By correlating the pressures of ice-VII inclusions with those of other high-pressure inclusions, we assess quantitatively the pressures and temperatures of their entrapment. We show that the ice-VII-bearing diamonds formed at depths down to 800 ± 60 km but at temperatures 200–500 K below average mantle temperature that match the pressure-temperature conditions of decomposing dense hydrous mantle silicates. Our work presents strong evidence for coupled recycling of water and carbon in the deep mantle based on natural samples.
- Published
- 2021
- Full Text
- View/download PDF
24. Development of High-Pressure Multigrain X-Ray Diffraction for Exploring the Earth’s Interior
- Author
-
Li Zhang, Hongsheng Yuan, Yue Meng, and Ho-Kwang Mao
- Subjects
Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for understanding deep mantle processes. Such high P–T experiments are commonly conducted in a laser-heated diamond anvil cell, producing a multiphase assemblage consisting of 100 nm to submicron crystallite grains. The structures of these lower mantle phases often cannot be preserved upon pressure quenching; thus, in situ characterization is needed. The X-ray diffraction (XRD) pattern of such a multiphase assemblage usually displays a mixture of diffraction spots and rings as a result of the coarse grain size relative to the small X-ray beam size (3–5 μm) available at the synchrotron facilities. Severe peak overlapping from multiple phases renders the powder XRD method inadequate for indexing new phases and minor phases. Consequently, structure determination of new phases in a high P–T multiphase assemblage has been extremely difficult using conventional XRD techniques. Our recent development of multigrain XRD in high-pressure research has enabled the indexation of hundreds of individual crystallite grains simultaneously through the determination of crystallographic orientations for these individual grains. Once indexation is achieved, each grain can be treated as a single crystal. The combined crystallographic information from individual grains can be used to determine the crystal structures of new phases and minor phases simultaneously in a multiphase system. With this new development, we have opened up a new area of crystallography under the high P–T conditions of the deep lower mantle. This paper explains key challenges in studying multiphase systems and demonstrates the unique capabilities of high-pressure multigrain XRD through successful examples of its applications. Keywords: High pressure, Synchrotron X-ray, Multigrain, Diamond anvil cell, Minerals, Petrology, Earth’s interior
- Published
- 2019
- Full Text
- View/download PDF
25. Temperature-induced amorphization in CaCO3 at high pressure and implications for recycled CaCO3 in subduction zones
- Author
-
Mingqiang Hou, Qian Zhang, Renbiao Tao, Hong Liu, Yoshio Kono, Ho-kwang Mao, Wenge Yang, Bin Chen, and Yingwei Fei
- Subjects
Science - Abstract
Subduction of oceanic crust introduces huge amounts of carbonates into Earth’s mantle, contributing to the global carbon cycle. Here, based on high-pressure-temperature experiments, the authors present a reversible temperature-induced transition from aragonite to amorphous CaCO3.
- Published
- 2019
- Full Text
- View/download PDF
26. Altered chemistry of oxygen and iron under deep Earth conditions
- Author
-
Jin Liu, Qingyang Hu, Wenli Bi, Liuxiang Yang, Yuming Xiao, Paul Chow, Yue Meng, Vitali B. Prakapenka, Ho-Kwang Mao, and Wendy L. Mao
- Subjects
Science - Abstract
Iron oxides prevail in the deep Earth, at extreme pressures and temperatures, with different stoichiometries than in ambient conditions. Here, high-pressure synchrotron X-ray spectroscopic measurements reveal the oxidation states of Fe and O in iron superoxide, shedding light on the puzzling chemistry of iron and oxygen in the deep Earth
- Published
- 2019
- Full Text
- View/download PDF
27. Acknowledgement to reviewers
- Author
-
Michel Koenig, Weiyan Zhang, and Ho-Kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Published
- 2021
- Full Text
- View/download PDF
28. Matter and radiation at extremes: Prospects and impacts
- Author
-
Michel Koenig, David Crandall, Ho-Kwang Mao, Ke Lan, Dieter H. H. Hoffmann, and Weiyan Zhang
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Published
- 2021
- Full Text
- View/download PDF
29. 2020—Transformative science in the pressure dimension
- Author
-
Ho-Kwang Mao, Bin Chen, Huiyang Gou, Kuo Li, Jin Liu, Lin Wang, Hong Xiao, and Wenge Yang
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Published
- 2021
- Full Text
- View/download PDF
30. Crystallography of low Z material at ultrahigh pressure: Case study on solid hydrogen
- Author
-
Cheng Ji, Bing Li, Wenjun Liu, Jesse S. Smith, Alexander Björling, Arnab Majumdar, Wei Luo, Rajeev Ahuja, Jinfu Shu, Junyue Wang, Stanislav Sinogeikin, Yue Meng, Vitali B. Prakapenka, Eran Greenberg, Ruqing Xu, Xianrong Huang, Yang Ding, Alexander Soldatov, Wenge Yang, Guoyin Shen, Wendy L. Mao, and Ho-Kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensed matter. However, the only way to determine crystal structures of materials above 100 GPa, namely, X-ray diffraction (XRD), especially for low Z materials, remains nontrivial in the ultrahigh-pressure region, even with the availability of brilliant synchrotron X-ray sources. In this work, we perform a systematic study, choosing hydrogen (the lowest X-ray scatterer) as the subject, to understand how to better perform XRD measurements of low Z materials at multimegabar pressures. The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254 GPa at room temperature [C. Ji et al., Nature 573, 558–562 (2019)]. We present our discoveries and experiences with regard to several aspects of this work, namely, diamond anvil selection, sample configuration for ultrahigh-pressure XRD studies, XRD diagnostics for low Z materials, and related issues in data interpretation and pressure calibration. We believe that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures, eventually testing structural models of metallic hydrogen.
- Published
- 2020
- Full Text
- View/download PDF
31. Key problems of the four-dimensional Earth system
- Author
-
Ho-kwang Mao and Wendy L. Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Compelling evidence indicates that the solid Earth consists of two physicochemically distinct zones separated radially in the middle of the lower mantle at ∼1800 km depth. The inner zone is governed by pressure-induced physics and chemistry dramatically different from the conventional behavior in the outer zone. These differences generate large physical and chemical potentials between the two zones that provide fundamental driving forces for triggering major events in Earth’s history. One of the main chemical carriers between the two zones is H2O in hydrous minerals that subducts into the inner zone, releases hydrogen, and leaves oxygen to create superoxides and form oxygen-rich piles at the core–mantle boundary, resulting in localized net oxygen gain in the inner zone. Accumulation of oxygen-rich piles at the base of the mantle could eventually reach a supercritical level that triggers eruptions, injecting materials that cause chemical mantle convection, superplumes, large igneous provinces, extreme climate changes, atmospheric oxygen fluctuations, and mass extinctions. Interdisciplinary research will be the key for advancing a unified theory of the four-dimensional Earth system.
- Published
- 2020
- Full Text
- View/download PDF
32. Everything you always wanted to know about metallic hydrogen but were afraid to ask
- Author
-
Eugene Gregoryanz, Cheng Ji, Philip Dalladay-Simpson, Bing Li, Ross T. Howie, and Ho-Kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
The hydrogen molecule is made from the first and lightest element in the periodic table. When hydrogen gas is either compressed or cooled, it forms the simplest molecular solid. This solid exhibits many interesting and fundamental physical phenomena. It is believed that if the density of the solid is increased by compressing it to very high pressures, hydrogen will transform into the lightest known metal with very unusual and fascinating properties, such as room temperature superconductivity and/or superfluidity. In this article, we provide a critical look at the numerous claims of hydrogen metallization and the current experimental state of affairs.
- Published
- 2020
- Full Text
- View/download PDF
33. Acknowledgement to reviewers
- Author
-
Weiyan Zhang and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Published
- 2020
- Full Text
- View/download PDF
34. Superconductivity in La and Y hydrides: Remaining questions to experiment and theory
- Author
-
Viktor Struzhkin, Bing Li, Cheng Ji, Xiao-Jia Chen, Vitali Prakapenka, Eran Greenberg, Ivan Troyan, Alexander Gavriliuk, and Ho-kwang Mao
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Recent reports of the superconductivity in hydrides of two different families (covalent lattice, as in SH3 and clathrate-type H-cages containing La and Y atoms, as in LaH10 and YH6) have revealed new families of high-Tc materials with Tc’s near room temperature values. These findings confirm earlier expectations that hydrides may have very high Tc’s due to the fact that light H atoms have very high vibrational frequencies, leading to high Tc values within the conventional Bardeen–Cooper–Schrieffer phonon mechanism of superconductivity. However, as is pointed out by Ashcroft, it is important to have the metallic hydrogen “alloyed” with the elements added to it. This concept of a metallic alloy containing a high concentration of metal-like hydrogen atoms has been instrumental in finding new high-Tc superhydrides. These new superhydride “room-temperature” superconductors are stabilized only at very high pressures above 100 GPa, making the experimental search for their superconducting properties very difficult. We will review the current experimental and theoretical results for LaH10−x and YH6−x superhydrides.
- Published
- 2020
- Full Text
- View/download PDF
35. Emergent superconductivity in an iron-based honeycomb lattice initiated by pressure-driven spin-crossover
- Author
-
Yonggang Wang, Jianjun Ying, Zhengyang Zhou, Junliang Sun, Ting Wen, Yannan Zhou, Nana Li, Qian Zhang, Fei Han, Yuming Xiao, Paul Chow, Wenge Yang, Viktor V. Struzhkin, Yusheng Zhao, and Ho-kwang Mao
- Subjects
Science - Abstract
Up to now, all iron-based high-T c superconductors contain a square iron lattice. Here, Wang et al. report the observation of superconductivity in an iron honeycomb lattice accompanied with pressure-driven spin-crossover, in-plane lattice collapse and insulator-metal transition.
- Published
- 2018
- Full Text
- View/download PDF
36. Future Study of Dense Superconducting Hydrides at High Pressure
- Author
-
Dong Wang, Yang Ding, and Ho-Kwang Mao
- Subjects
superconductivity ,hydrides ,high pressure ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
The discovery of a record high superconducting transition temperature (Tc) of 288 K in a pressurized hydride inspires new hope to realize ambient-condition superconductivity. Here, we give a perspective on the theoretical and experimental studies of hydride superconductivity. Predictions based on the BCS–Eliashberg–Midgal theory with the aid of density functional theory have been playing a leading role in the research and guiding the experimental realizations. To date, about twenty hydrides experiments have been reported to exhibit high-Tc superconductivity and their Tc agree well with the predicted values. However, there are still some controversies existing between the predictions and experiments, such as no significant transition temperature broadening observed in the magnetic field, the experimental electron-phonon coupling beyond the Eliashberg–Midgal limit, and the energy dependence of density of states around the Fermi level. To investigate these controversies and the origin of the highest Tc in hydrides, key experiments are required to determine the structure, bonding, and vibrational properties associated with H atoms in these hydrides.
- Published
- 2021
- Full Text
- View/download PDF
37. Synthesis of quenchable amorphous diamond
- Author
-
Zhidan Zeng, Liuxiang Yang, Qiaoshi Zeng, Hongbo Lou, Hongwei Sheng, Jianguo Wen, Dean J. Miller, Yue Meng, Wenge Yang, Wendy L. Mao, and Ho-kwang Mao
- Subjects
Science - Abstract
Diamond’s properties are dictated by its crystalline, fully tetrahedrally bonded structure. Here authors synthesize a bulk sp 3-bonded amorphous form of carbon under high pressure and temperature, show that it has bulk modulus comparable to crystalline diamond and that it can be recovered under ambient conditions.
- Published
- 2017
- Full Text
- View/download PDF
38. Local structure of liquid gallium under pressure
- Author
-
Renfeng Li, Luhong Wang, Liangliang Li, Tony Yu, Haiyan Zhao, Karena W. Chapman, Yanbin Wang, Mark L. Rivers, Peter J. Chupas, Ho-kwang Mao, and Haozhe Liu
- Subjects
Medicine ,Science - Abstract
Abstract In situ high energy X-ray pair distribution function (PDF) measurements, microtomography and reverse Monte Carlo simulations were used to characterize the local structure of liquid gallium up to 1.9 GPa. This pressure range includes the well-known solid-solid phase transition from Ga-I to Ga-II at low temperature. In term of previous research, the local structure of liquid gallium within this domain was suggested a mixture of two local structures, Ga I and Ga II, based on fitting experimental PDF to known crystal structure, with a controversy. However, our result shows a distinctly different result that the local structure of liquid gallium resembles the atomic arrangement of both gallium phase II and III (the high pressure crystalline phase). A melting mechanism is proposed for Ga, in which the atomic structure of phase Ι breaks up at the onset of melting, providing sufficient free volume for atoms to rearrange, to form the melt.
- Published
- 2017
- Full Text
- View/download PDF
39. Synthesis of sodium polyhydrides at high pressures
- Author
-
Viktor V. Struzhkin, Duck Young Kim, Elissaios Stavrou, Takaki Muramatsu, Ho-kwang Mao, Chris J. Pickard, Richard J. Needs, Vitali B. Prakapenka, and Alexander F. Goncharov
- Subjects
Science - Abstract
The only known compound of sodium and hydrogen is ionic NaH, but theory predicts the existence of polyhydrides at high pressure. Here, the authors report observations of the formation of polyhydrides above 40 GPa and 2000 K, supporting the idea of multicentre bonding in a material with unusual stoichiometry.
- Published
- 2016
- Full Text
- View/download PDF
40. Recent advances in high-pressure science and technology
- Author
-
Ho-Kwang Mao, Bin Chen, Jiuhua Chen, Kuo Li, Jung-Fu Lin, Wenge Yang, and Haiyan Zheng
- Subjects
Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Recently we are witnessing the boom of high-pressure science and technology from a small niche field to becoming a major dimension in physical sciences. One of the most important technological advances is the integration of synchrotron nanotechnology with the minute samples at ultrahigh pressures. Applications of high pressure have greatly enhanced our understanding of the electronic, phonon, and doping effects on the newly emerged graphene and related 2D layered materials. High pressure has created exotic stoichiometry even in common Group 17, 15, and 14 compounds and drastically altered the basic σ and π bonding of organic compounds. Differential pressure measurements enable us to study the rheology and flow of mantle minerals in solid state, thus quantitatively constraining the geodynamics. They also introduce a new approach to understand defect and plastic deformations of nano particles. These examples open new frontiers of high-pressure research.
- Published
- 2016
- Full Text
- View/download PDF
41. Structural stability of methane hydrate at high pressures
- Author
-
Jinfu Shu, Xiaojia Chen, I.-Ming Chou, Wenge Yang, Jingzhu Hu, Russell J. Hemley, and Ho-kwang Mao
- Subjects
Methane hydrate ,Structural stability ,High pressure ,Geology ,QE1-996.5 - Abstract
The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I, II, and H in diamond-anvil cells. The diffraction data for types II (sII) and H (sH) were refined to the known structures with space groups Fd3m and P63/mmc, respectively. Upon compression, sI methane hydrate transforms to the sII phase at 120 MPa, and then to the sH phase at 600 MPa. The sII methane hydrate was found to coexist locally with sI phase up to 500 MPa and with sH phase up to 600 MPa. The pure sH structure was found to be stable between 600 and 900 MPa. Methane hydrate decomposes at pressures above 3 GPa to form methane with the orientationally disordered Fm3m structure and ice VII (Pn3m). The results highlight the role of guest (CH4)-host (H2O) interactions in the stabilization of the hydrate structures under pressure.
- Published
- 2011
- Full Text
- View/download PDF
42. Spin quenching assisted by a strongly anisotropic compression behavior in MnP
- Author
-
Fei Han, Di Wang, Yonggang Wang, Nana Li, Jin-Ke Bao, Bing Li, Antia S Botana, Yuming Xiao, Paul Chow, Duck Young Chung, Jiuhua Chen, Xiangang Wan, Mercouri G Kanatzidis, Wenge Yang, and Ho-Kwang Mao
- Subjects
superconductivity ,high pressure ,spin state ,structural distortion ,Science ,Physics ,QC1-999 - Abstract
We studied the crystal structure and spin state of MnP under high pressure with synchrotron x-ray diffraction and x-ray emission spectroscopy (XES). MnP has an exceedingly strong anisotropy in compressibility, with the primary compressible direction along the b axis of the Pnma structure. XES reveals a pressure-driven quenching of the spin state in MnP. First-principles calculations suggest that the strongly anisotropic compression behavior significantly enhances the dispersion of the Mn d -orbitals and the splitting of the d -orbital levels compared to the hypothetical isotropic compression behavior. Thus, we propose spin quenching results mainly from the significant enhancement of the itinerancy of d electrons and partly from spin rearrangement occurring in the split d -orbital levels near the Fermi level. This explains the fast suppression of magnetic ordering in MnP under high pressure. The spin quenching lags behind the occurrence of superconductivity at ∼8 GPa implying that spin fluctuations govern the electron pairing for superconductivity.
- Published
- 2018
- Full Text
- View/download PDF
43. In Situ High-Pressure Correlated Transportation of Heavy Rare-Earth Perovskite Nickelates as Batch Synthesized within Eutectic Molten Salts at MPa-pO2.
- Author
-
Yuchen Cui, Jingxin Gao, Hongliang Dong, Ziang Li, Ziyou Zhang, Vei Wang, Kaiqi Nie, Zeng, Zhidan, Yong Jiang, Nuofu Chen, Ho-kwang Mao, and Jikun Chen
- Published
- 2024
- Full Text
- View/download PDF
44. Iron silicate perovskite and postperovskite in the deep lower mantle.
- Author
-
Ziqiang Yang, Zijun Song, Zhongqing Wu, Ho-kwang Mao, and Li Zhang
- Subjects
IRON silicates ,EARTH'S mantle ,PEROVSKITE ,FRICTION velocity ,GEOCHEMICAL modeling - Abstract
Ferromagnesian silicates are the dominant constituents of the Earth's mantle, which comprise more than 80% of our planet by volume. To interpret the low shear-velocity anomalies in the lower mantle, we need to construct a reliable transformation diagram of ferromagnesian silicates over a wide pressure-temperature (P-T) range. While MgSiO
3 in the perovskite structure has been extensively studied due to its dominance on Earth, phase transformations of iron silicates under the lower mantle conditions remain unresolved. In this study, we have obtained an iron silicate phase in the perovskite (Pv) structure using synthetic fayalite (Fe2SiO4) as the starting material under P-T conditions of the lower mantle. Chemical analyses revealed an unexpectedly high Fe/Si ratio of 1.72(3) for the Pv phase in coexistence with metallic iron particles, indicating incorporation of about 25 mol% Fe2O3 in the Pv phase with an approximate chemical formula (Fe2+ 0.75Fe3+ 0.25)(Fe3+ 0.25Si0.75)O3 . We further obtained an iron silicate phase in the postperovskite (PPv) structure above 95 GPa. The calculated curves of compressional (VP) and shear velocity (VS) of iron silicate Pv and PPv as a function of pressure are nearly parallel to those of MgSiO3, respectively. To the best of our knowledge, the iron silicate Pv and PPv are the densest phases among all the reported silicates stable at P-T conditions of the lower mantle. The high ferric iron content in the silicate phase and the spin-crossover of ferric iron at the Si-site above ~55 GPa should be taken into account in order to interpret the seismic observations. Our results would provide crucial information for constraining the geophysical and geochemical models of the lower mantle. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
45. Arylazo under Extreme Conditions: [2 + 2] Cycloaddition and Azo Metathesis
- Author
-
Dexiang Gao, Xingyu Tang, Chunfang Zhang, Yajie Wang, Xin Yang, Peijie Zhang, Xuan Wang, Jingqin Xu, Jie Su, Fuyang Liu, Xiao Dong, Xiaohuan Lin, Bao Yuan, Nozomu Hiraoka, Haiyan Zheng, Le Kang, Kuo Li, and Ho-kwang Mao
- Subjects
General Energy ,Physical and Theoretical Chemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2023
46. Piezovoltaics from PdHx
- Author
-
Yida Wang, Guangwei Che, Xin Yang, Jie Zheng, Youyu Lin, Haiyan Zheng, Kuo Li, and Ho-kwang Mao
- Subjects
General Materials Science ,Physical and Theoretical Chemistry - Published
- 2023
47. Ordered Van der Waals Hetero-nanoribbon from Pressure-Induced Topochemical Polymerization of Azobenzene
- Author
-
Peijie Zhang, Dexiang Gao, Xingyu Tang, Xin Yang, Haiyan Zheng, Yida Wang, Xuan Wang, Jingqin Xu, Zijia Wang, Jie Liu, Xiaoge Wang, Jing Ju, Mingxue Tang, Xiao Dong, Kuo Li, and Ho-kwang Mao
- Subjects
Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Published
- 2023
48. Intrinsic Zero-Linear and Zero-Area Compressibilities over an Ultrawide Pressure Range within a Gear-Spring Structure
- Author
-
Dequan Jiang, Ting Wen, Huimin Song, Zimin Jiang, Chen Li, Ke Liu, Wenge Yang, Ho-kwang Mao, and Yonggang Wang
- Subjects
General Chemistry - Published
- 2022
49. Preservation of high-pressure volatiles in nanostructured diamond capsules
- Author
-
Zhidan Zeng, Jianguo Wen, Hongbo Lou, Xin Zhang, Liuxiang Yang, Lijie Tan, Benyuan Cheng, Xiaobing Zuo, Wenge Yang, Wendy L. Mao, Ho-kwang Mao, and Qiaoshi Zeng
- Subjects
Multidisciplinary - Abstract
High pressure induces dramatic changes and novel phenomena in condensed volatiles
- Published
- 2022
50. Quantifying the partial ionization effect of gold in the transition region between condensed matter and warm dense matter
- Author
-
Zhiguo Li, Xiang Wang, Yong Hou, Yuying Yu, Guojun Li, Long Hao, Xuhai Li, Huayun Geng, Chengda Dai, Qiang Wu, Ho-Kwang Mao, and Jianbo Hu
- Subjects
Multidisciplinary - Abstract
It is now well known that solids under ultra-high-pressure shock compression will enter the warm dense matter (WDM) regime which connects condensed matter and hot plasma. How condensed matter turns into the WDM, however, remains largely unexplored due to the lack of data in the transition pressure range. In this letter, by employing the unique high-Z three-stage gas gun launcher technique developed recently, we compress gold into TPa shock pressure to fill the gap inaccessible by the two-stage gas gun and laser shock experiments. With the aid of high-precision Hugoniot data obtained experimentally, we observe a clear softening behavior beyond ~560 GPa. The state-of-the-art ab-initio molecular dynamics calculations reveal that the softening is caused by the ionization of 5d electrons in gold. This work quantifies the partial ionization effect of electrons under extreme conditions, which is critical to model the transition region between condensed matter and WDM.
- Published
- 2023
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.