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Modeling and Numerical Simulation of Material Science 2013年第4期3卷 158-169页

作者： Ian D. R. Mackinnon Jose A. Alarco Peter C. Talbot Institute for Future Environments Brisbane Australia Science and Engineering Faculty School of Chemistry Physics and Mechanical Engineering Queensland University of Technology Brisbane Australia

Comparison of well-determined single crystal data for stoichiometric, or near-stoichiometric, metal hexaborides confirms previously identified lattice parameter trends using powder diffraction. Trends for both divalent and trivalent forms suggest that potential new forms for synthesis include Sc and Mn hexaborides. Density Functional Theory (DFT) calculations for KB6, CaB6, YB6, LaB6, boron octahedral clusters and Sc and Mn forms show that the shapes of bonding orbitals are defined by the boron framework. Inclusion of metal into the boron framework induces a reduction in energy ranging from 1 eV to 6 eV increasing with ionic charge. For metals with d1 character, such a shift in energy brings a doubly degenerate band section along with the G-M reciprocal space direction within the conduction bands tangential to the Fermi surface. ScB6 band structure and density of states calculations show directions and gap characteristics similar to those of YB6 and LaB6. These calculations for ScB6 suggest that it may be possible to realize superconductivity in this compound if synthesized.

关键词： Metal hexaborides Electronic Structure Superconductivity Boron Framework

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Nanocrystalline high-entropy hexaboride ceramics enable remarkable performance as thermionic emission cathodes

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Fundamental Research 2023年第6期3卷 979-987页

作者： Mengdong Ma Xinyu Yang Hong Meng Zhisheng Zhao Julong He Yanhui Chu School of Materials Science and Engineering South China University of TechnologyGuangzhou 510641China Center for High Pressure Science(CHiPS) State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China School of Materials Science and Engineering Hefei University of TechnologyHefei 230009China

The development of high-entropy borides with combined structural and functional performance holds untold scientific and technological potential,yet relevant studies have been rarely *** this work,we report nanocrystalline(La_(0.25)Ce_(0.25)Nd_(0.25)Eu_(0.25))B6 high-entropy rare-earth hexaboride(HEReB6-1)ceramics fabricated through the high-pressure sintering of self-synthesized nanopowders for the first *** as-fabricated samples exhibited a highly dense(96.3%)nanocrystalline(94 nm)microstructure with major(001)fiber textures and good grain boundaries without any impurities,resulting in a remarkable mechanical,electrical,and thermionic emission *** results showed that the samples possessed outstanding comprehensive mechanical properties and a high electrical resistivity from room temperature to high temperatures;these were greater than the average values of corresponding binary rare-earth hexaborides,such as a Vickers hardness of 23.4±0.6 GPa and a fracture toughness of 3.0±0.4 MPa•m^(1/2)at room *** importantly,they showed high emission current densities at elevated temperatures,which were higher than the average values of the corresponding binary rare-earth *** instance,the maximum emission current density reached 48.3 A•cm^(−2)at 1873 *** superior performance makes the nanocrystalline HEReB6-1 ceramics highly suitable for potential applications in thermionic emission cathodes.

关键词： High-entropy ceramics hexaborides Nanocrystalline Mechanical properties Thermionic emission

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Comparison of Functionals for Metal Hexaboride Band Structure Calculations

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Modeling and Numerical Simulation of Material Science 2014年第2期4卷 53-69页

作者： Jose A. Alarco Peter C. Talbot Ian D. R. Mackinnon Institute for Future Environments Queensland University of Technology Gardens Point Campus BrisbaneAustralia Institute for Future Environments Queensland University of Technology Gardens Point Campus BrisbaneAustralia Science and Engineering Faculty Queensland University of Technology Gardens Point Campus BrisbaneAustralia

Density functional calculations of the electronic band structure for superconducting and semiconducting metal hexaborides are compared using a consistent suite of assumptions and with emphasis on the physical implications of computed models. Spin polarization enhances mathematical accuracy of the functional approximations and adds significant physical meaning to model interpretation. For YB6 and LaB6, differences in alpha and beta projections occur near the Fermi energy. These differences are pronounced for superconducting hexaborides but do not occur for other metal hexaborides.

关键词： hexaborides Density Functional Theory Band Structure Spin Polarization Superconductivity

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