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4. Pressure-driven switching of magnetism in layered CrCl3

Author

Ahmad, Azkar Saeed, Liang, Yongcheng, Dong, Mingdong, Zhou, Xuefeng, Fang, Leiming, Xia, Yuanhua, Dai, Jianhong, Yan, Xiaozhi, Yu, Xiaohui, Zhang, Guojun, Zhao, Yusheng, and Wang, Shanmin

Subjects
Condensed Matter - Materials Science
Abstract

Layered transition-metal compounds with controllable magnetic behaviors provide many fascinating opportunities for the fabrication of high-performance magneto-electric and spintronic devices. The tuning of their electronic and magnetic properties is usually limited to the change of layer thickness, electrostatic doping, and the control of electric and magnetic fields. However, pressure has been rarely exploited as a control parameter for tailoring their magneto-electric properties. Here, we report a unique pressure-driven isostructural phase transition in layered CrCl3 accompanied by a simultaneous switching of magnetism from a ferromagnetic to an antiferromagnetic ordering. Our experiments, in combination with ab initio calculations, demonstrate that such a magnetic transformation hinders the band-gap collapse under pressure, leading to an anomalous semiconductor-to-semiconductor transition. Our findings not only reveal high potential of CrCl3 in electronic and spintronic applications under ambient and extreme conditions but also establish the basis for exploring unusual phase transitions in layered transition-metal compounds.

Published
2019

10. Identification of a monoclinic metallic state in VO2 from a modified first-principles approach

Author

Liang, Yongcheng, Qin, Ping, Liang, Zhiyong, Yuan, Xun, and Zhang, Yubo

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

Metal-insulator transition underlies many remarkable and technologically important phenomena in VO2. Even though its monoclinic structure had before been the reserve of the insulating state, recent experiments have observed an unexpected monoclinic metallic state. Here we use a modified approach combining first-principles calculations with orbital-biased potentials to reproduce the correct stability ordering and electronic structure of different phases of VO2. We identify a ferromagnetic monoclinic metal that is likely to be the experimentally observed mysterious metastable state. Furthermore, our calculations show that an isostructural insulator-metal electronic transition is followed by the lattice distortion from the monoclinic structure to the rutile structure. These results not only explain the experimental observations of the monoclinic metallic state and the decoupled structural and electronic transitions of VO2, but also provide a understanding for the metal-insulator transition in other strongly correlated d electron systems.

Published
2016
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19. Novel Tungsten Triboride

Author

Liang, Yongcheng and on, so

Subjects
Condensed Matter - Materials Science
Abstract

A highly stable tungsten triboride with the Pearson symbol hP24 (hP24-WB3) is identified by using density functional theory calculations. This new structure can be derived from the well-known hP3 configuration by removing one third of tungsten atoms systematically so that the remaining tungsten atoms form three cycled layers of open hexagons with each a layer displaced by one atom. Such a porous and metallic system has an unexpectedly high Vickers hardness of 38.3 GPa. It is revealed that a three-dimensional covalent framework composed of hexagonal boron planes interconnected with strong zigzag W-B bonds is responsible for its unusual high hardness.

Published
2012
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21. Theoretical Evidence for the Berry-Phase Mechanism of Anomalous Hall Transport: First-principles Studies on CuCr$_2$Se$_{4-x}$Br$_x$

Author

Yao, Yugui, Liang, Yongcheng, Xiao, Di, Niu, Qian, Shen, Shun-Qing, Dai, X., and Fang, Zhong

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

To justify the origin of anomalous Hall effect (AHE), it is highly desirable to have the system parameters tuned continuously. By quantitative calculations, we show that the doping dependent sign reversal in CuCr$_{2}$Se$_{4-x}$Br$_{x}$, observed but not understood, is nothing but direct evidence for the Berry-Phase mechanism of AHE. The systematic calculations well explain the experiment data for the whole doping range where the impurity scattering rates is changed by several orders with Br substitution. Further sign change is also predicted, which may be tested by future experiments., Comment: 4 pages

Published
2006
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22. FRACTURE CRITERION OF THE THEORY OF CRITICAL DISTANCE FOR NOTCHES

Author

LIU XiaoMei, BIAN YongMing, LIANG YongCheng, and LI AnHu

Subjects
The theory of critical distance, Fracture toughness, Graphite, Notches, Mechanical engineering and machinery, TJ1-1570, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

Whether the brittle fracture criterion of theory of critical distance is suitable for graphite plates with different shape notches was studied by means of analysis of finite element: including tensile specimens with U notches,blunted V-notch specimens of semi-circular bend,three-point bending specimens with single V-notch and compressed specimens of Brazilian disk.According to the theory of critical distance,the parameters of fracture toughness for two graphite materials were calculated by the calibrated characteristic distance and inherent strength and compared with the given values in the literature. The values of fracture loading for all notches under mode I were predicted and also compared with the experimental values. The theory of critical distance can not only predict the fracture loading and but also provide an engineering method to evaluate the fracture toughness by the fracture experiment of notched components. The theory of critical distance suitable for engineering just makes use of the numerical results,avoiding the complex analytical solutions of stress fields near the tip of notches,which is the best advantage.

Published
2018
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28. A METHOD MEASURING FRACTURE PARAMETERS OF BRITTLE MATERIAL USING U-NOTCHES

Author

LIU XiaoMei, BIAN YongMing, and LIANG YongCheng

Subjects
U-notch, Brittle fracture criterion, Critical fracture loading, Fracture toughness, Tensile strength, Mechanical engineering and machinery, TJ1-1570, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

Based on two stress criterions（ the maximum circumferential stress criterion and average circumferential stress criterion） for U-notches under Mode-I,relationships among the critical notch stress intensity factor,the fracture toughness and the tensile strength were built separately,which follows the similar idea of Seweryn regarding the crack as a special U-notch with the notch radius equaling to zero. By means of the critical fracture loadings for U-notched plates under Mode-I and the finite element results of Ansys,a new method has been proposed to measure the fracture toughness and the tensile strength. The three point bending and tensile experiments in related references of PMMA and aluminum alloy specimens with single-edged U-notch and graphite tensile plates with central U-notch were verified. It indicates that the methods are simple and can be applied in engineering because the U notches can be machined conveniently and the fracture load under Mode-I can also be obtained easily.

Published
2015
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30. ZrB2‐based solid solution ceramics and their mechanical and thermal properties.

Author

Wu, Yue, Bao, Weichao, Shen, Xiao‐Qin, Liu, Ji‐Xuan, Qin, Yuan, Liang, Yongcheng, Xu, Fangfang, and Zhang, Guo‐Jun

Subjects
SOLID solutions, THERMAL properties, HIGH temperatures, PHONON scattering, THERMAL conductivity, POWDERS, CERAMICS
Abstract

Zirconium diboride ceramics as one of the main members of ultrahigh‐temperature ceramics are capable of being used as structural components at ultrahigh temperatures. Entropy adjusting is a newly developed approach to improving the properties of ceramics. In this work, a series of ZrB2‐based solid solution ceramics with different mixing entropies, formulated (ZrxTiyNbyTay)B2 (x =.25,.85,.925,.9625, 1; x + 3y = 1), were prepared by adjusting the content of other diborides. Diboride solid solution powders were synthesized by boro/carbothermal reduction process and then densified by spark plasma sintering. The results show that the formation of a single‐phase solid solution is independent of the mixing entropy in (ZrxTiyNbyTay)B2 system. The addition of other diborides into ZrB2 is beneficial to reduce the particle size of the synthesized powder and promote the densification process. The dense sintered samples with higher mixing entropy have finer grain size, higher hardness, and modulus. The (Zr0.25Ti0.25Nb0.25Ta0.25)B2 ceramic has the highest hardness of 31 GPa and a modulus of 682 GPa. Severe lattice distortion in samples with higher mixing entropy will result in increased phonon scattering and lower thermal conductivity. [ABSTRACT FROM AUTHOR]

Published
2023
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33. BEM-based algorithm for composite materials with Gurtin–Murdoch interfaces: Error analysis and effective parameters.

Author

Han, Zhilin, Gu, Yankai, Liang, Yongcheng, and Zheng, Xingwei

Subjects
COMPOSITE materials, BOUNDARY element methods, PHYSICAL constants, ALGORITHMS
Abstract

The effective parameters of the composite materials with Gurtin–Murdoch ((G-M) interfaces are analyzed by standard boundary element method (BEM)-based equivalent inhomogeneity technique (EIT). The physical quantities all over the domain are first compared with the analytical and semi-analytical results to validate accuracy. The effective parameters are then obtained by the present numerical EIT. Since interactions have been considered, we believe our results are more accurate than traditional estimations, such as the generalized self-consistent model (GSCM). Due to the numerical treatment is performed to the present method is more flexible to simulate the effective parameters of clusters with complex geometries. [ABSTRACT FROM AUTHOR]

Published
2022
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34. Enhanced Hardness in Transition-Metal Monocarbides via Optimal Occupancy of Bonding Orbitals

Author

Liang, Yongcheng, primary, Wei, Xiao-Feng, additional, Gu, Chao, additional, Liu, Ji-Xuan, additional, Li, Fei, additional, Yan, Mingqi, additional, Zheng, Xingwei, additional, Han, Zhilin, additional, Zhao, Yusheng, additional, Wang, Shanmin, additional, Yang, Jiong, additional, Zhang, Wenqing, additional, Kou, Liangzhi, additional, and Zhang, Guo-Jun, additional

Published
2021
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37. Isosymmetric phase transitions, ultrahigh ductility, and topological nodal lines in $α−Ag_{2}S$

Author

Liang, Yongcheng, Ahmad, Azkar Saeed, Zhao, Jianzhou, Song, Guozhu, Zhou, Xuefeng, Ji, Jialin, Zhang, Wei, Han, Zhilin, Liu, Jixuan, Stahl, Kenny, Pakhomova, Anna, Glazyrin, Konstantin, Zhang, Guo-Jun, Zhang, Wenqing, Zhao, Yusheng, Yu, Rui, Wang, Shanmin, and Zhang, Peihong

Subjects
Condensed Matter::Materials Science, ddc:530
Abstract

Physical review / B 102(14), 140101 (2020). doi:10.1103/PhysRevB.102.140101, We report two reversible pressure-induced isosymmetric phase transitions in $α−Ag_{2}S$ that are accompanied by two compressive anomalies at 7.5 and 16 GPa, respectively. The first transition arises from a sudden and drastic puckering of the wrinkled Ag-S layers, which leads to an anomalous structural softening at high pressure and gives rise to the ultrahigh compressive ductility in $α−Ag_{2}S$. The second transition stems from a pressure-driven electronic state crossover from a conventional semiconductor to a topological metal. The band-crossing points near the Fermi energy form a nodal-line structure due to the preservation of the time-reversal and space-inversion symmetries under pressure. Our findings not only reveal the underlying mechanism responsible for the ultrahigh ductility in this class of inorganic semiconductors, but also provide a distinctive member to the growing family of topological metals and semimetals., Published by Inst., Woodbury, NY

Published
2020

38. Isosymmetric phase transitions, ultrahigh ductility, and topological nodal lines in α- A g2 S

Author

Liang, Yongcheng, Ahmad, Azkar Saeed, Zhao, Jianzhou, Song, Guozhu, Zhou, Xuefeng, Ji, Jialin, Zhang, Wei, Han, Zhilin, Liu, Jixuan, Ståhl, Kenny, Pakhomova, Anna, Glazyrin, Konstantin, Zhang, Guo Jun, Zhang, Wenqing, Zhao, Yusheng, Yu, Rui, Wang, Shanmin, and Zhang, Peihong

Subjects
Condensed Matter::Materials Science
Abstract

We report two reversible pressure-induced isosymmetric phase transitions in α-Ag2S that are accompanied by two compressive anomalies at 7.5 and 16 GPa, respectively. The first transition arises from a sudden and drastic puckering of the wrinkled Ag-S layers, which leads to an anomalous structural softening at high pressure and gives rise to the ultrahigh compressive ductility in α-Ag2S. The second transition stems from a pressure-driven electronic state crossover from a conventional semiconductor to a topological metal. The band-crossing points near the Fermi energy form a nodal-line structure due to the preservation of the time-reversal and space-inversion symmetries under pressure. Our findings not only reveal the underlying mechanism responsible for the ultrahigh ductility in this class of inorganic semiconductors, but also provide a distinctive member to the growing family of topological metals and semimetals.

Published
2020

39. Isosymmetric phase transitions, ultrahigh ductility, and topological nodal lines in α−Ag2S

Author

Liang, Yongcheng, primary, Ahmad, Azkar Saeed, additional, Zhao, Jianzhou, additional, Song, Guozhu, additional, Zhou, Xuefeng, additional, Ji, Jialin, additional, Zhang, Wei, additional, Han, Zhilin, additional, Liu, Jixuan, additional, Stahl, Kenny, additional, Pakhomova, Anna, additional, Glazyrin, Konstantin, additional, Zhang, Guo-Jun, additional, Zhang, Wenqing, additional, Zhao, Yusheng, additional, Yu, Rui, additional, Wang, Shanmin, additional, and Zhang, Peihong, additional

Published
2020
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41. Strain stiffening, high load-invariant hardness, and electronic anomalies of boron phosphide under pressure

Author

Gui, Rui, primary, Xue, Zhe, additional, Zhou, Xuefeng, additional, Gu, Chao, additional, Ren, Xiangting, additional, Cheng, Hu, additional, Ma, Dejiang, additional, Qin, Jiaqian, additional, Liang, Yongcheng, additional, Yan, Xiaozhi, additional, Zhang, Jianzhong, additional, Zhang, Xinyu, additional, Yu, Xiaohui, additional, Wang, Liping, additional, Zhao, Yusheng, additional, and Wang, Shanmin, additional

Published
2020
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42. Pressure-driven switching of magnetism in layered CrCl3

Author

Ahmad, Azkar Saeed, primary, Liang, Yongcheng, additional, Dong, Mingdong, additional, Zhou, Xuefeng, additional, Fang, Leiming, additional, Xia, Yuanhua, additional, Dai, Jianhong, additional, Yan, Xiaozhi, additional, Yu, Xiaohui, additional, Dai, Junfeng, additional, Zhang, Guo-jun, additional, Zhang, Wenqing, additional, Zhao, Yusheng, additional, and Wang, Shanmin, additional

Published
2020
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