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Comparative first-principles study of elastic constants of covalent and ionic materials with LDA,GGA,and meta-GGA functionals and the prediction of mechanical hardness

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Science China(Technological Sciences) 2021年第12期64卷 2755-2761页

作者： XING WanDong MENG FanYan NING JinLiang SUN JianWei YU Rong Department of Physics University of Science and Technology BeijingBeijing 100083China National Center for Electron Microscopy in Beijing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Department of Physics and Engineering Physics Tulane UniversityNew OrleansLA 70118USA

Accurate prediction of single-crystal elastic constants is critical for materials design and for understanding phase transition and elastic interactions in *** this work,the accuracy of elastic constants calculated with three density functional approximations has been compared,including the local density approximation(LDA),the generalized gradient approximation(GGA),and the recently developed strongly constrained and appropriately normed(SCAN)*** results show that SCAN and PBE describe elastic constants better than *** strong correlation between the mechanical hardness and the stiffness of the softest eigenmode(SSE)has been given for above three density *** correlation is capable of predicting accurately the hardness of covalent,ionic,and mixed covalent-ionic crystals,and providing us a convenient indicator for the discovery of hard or superhard materials.

关键词： hardness indicator elastic constants stiffness of softest eigenmode superhard materials

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Is the hardness of material harder than diamond reliable?

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Journal of materials Science & Technology 2023年第13期144卷 111-117页

作者： Jin Liu Yongtao Zou Guodong David Zhan Pei Wang Xiaozhi Yan Duanwei He Liping Wang Institute of Atomic and Molecular Physics Sichuan UniversityChengdu 610065China School of Mechanical Engineering Jingchu University of TechnologyJingmen 448000China Academy for Advanced Interdisciplinary Studies and Department of PhysicsSouthern University of Science and TechnologyShenzhen 518055China Shenzhen Key Laboratory of Ultraintense Laser&Advanced Material Technology College of Engineering Physicsand Center for Advanced Material Diagnostic TechnologyShenzhen Technology UniversityShenzhen 518118China Drilling Technology Division Exploration and Petroleum Engineering Center-Advanced Research Center(EXPEC ARC)Saudi AramcoDhahran 31311Saudi Arabia

With the development of new synthesis methods and chemistries,a number of new superhard materials have been reported to be harder than *** such materials are highly desirable due to their wide-ranging applications,there are some inherent uncertainties in the methods utilized to determine and define the hardness of such *** this paper,we employed the standard Vickers diamond indenter and substitute indenters with the same shape to measure the hardness of nine ceramics and superhard materials within well-defined criteria and methodology,for the assessment of consistency in the hardness *** findings and the developed testing method in the current study have broad implications in characterizing new and emerging superhard materials,leading to new discoveries.

关键词： Vickers hardness superhard materials Emerging materials Applicability

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Effects of High Pressure on BC3

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Chinese Physics Letters 2006年第9期23卷 2538-2541页

作者：周金玲崔田马琰铭刘志明刘冰冰邹广田 National Laboratory of superhard materials Jilin University Changchun 130012

High-pressure phases of BC3 are studied within the local density approximation under the density functional theory framework. When the pressure reaches 20 GPa, the layered BC3 that is a semiconductor at ambient pressure, becomes metallic. As the pressure increases, the material changes into a network structure at about 35 GPa. To understand the mechanism of phase transitions, band structure and density of states are discussed. With the increase of pressure, the width of bands broadens and the dispersion of bands enlarges. Additionally, the density of states of the network bears great resemblance to that of diamond. Formation of the sp3 bonding in the network is the main reason for the structural transformation at 35 GPa.

关键词： GRAPHITE-LIKE MATERIAL STRUCTURAL-PROPERTIES superhard materials STATES FILMS

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Temperature-dependent hardness of zinc-blende structured covalent materials

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Science China materials 2021年第9期64卷 2280-2288页

作者： Xing Feng Jianwei Xiao Bin Wen Jijun Zhao Bo Xu Yanbin Wang Yongjun Tian Center for High Pressure Science State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China Key Laboratory of materials Modification by Laser Ion and Electron Beams(Ministry of Education)Dalian University of TechnologyDalian 116024China Center for Advanced Radiation Sources University of ChicagoChicagoIllinois 60439USA

Understanding the temperature-dependent hardness of covalent materials is of fundamental scientific interest and crucial technical *** we propose a temperature-dependent hardness formula for zinc-blende structured covalent materials based on the dislocation *** results indicate that at low temperatures,the Vickers hardness is primarily modulated by Poisson’s ratio and the shear modulus,with the latter playing a dominant *** an increase in temperature,the governing mechanism for the plastic deformation switches from shuffle-set dislocation control to glide-set dislocation control,and the hardness decreases precipitously at elevated ***,the intrinsic parameter a3G is revealed for zinc-blende structured covalent materials,which represents the resistance of a material to softening at high *** temperaturedependent hardness model agrees remarkably well with the experimental data of zinc-blende structured covalent *** work not only sheds light on the physical origin of hardness,but also provides a practical guide for the design of superhard materials.

关键词： hardness temperature effect dislocation covalent materials superhard materials

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