Revealing the Pressure-Induced Softening/Weakening Mechanism in Representative Covalent Materials
Tengfei Xu1,2, Shihao Zhang1,2, Dominik Legut3, Stan Veprek4, and Ruifeng Zhang1,2*
1School of Materials Science and Engineering, Beihang University, Beijing 100191, China 2Center for Integrated Computational Engineering (International Research Institute for Multidisciplinary Science) and Key Laboratory of High-Temperature Structural Materials & Coatings Technology (Ministry of Industry and Information Technology), Beihang University, Beijing 100191, China 3IT4Innovations, VSB-Technical University of Ostrava, 17 listopadu 2172/15, 708 00 Ostrava, Czech Republic 4Department of Chemistry, Technical University Munich, Lichtenbergstr 4, D-85747 Garching, Germany
Abstract：Diamond, cubic boron nitride (c-BN), silicon (Si), and germanium (Ge), as examples of typical strong covalent materials, have been extensively investigated in recent decades, owing to their fundamental importance in material science and industry. However, an in-depth analysis of the character of these materials' mechanical behaviors under harsh service environments, such as high pressure, has yet to be conducted. Based on several mechanical criteria, the effect of pressure on the mechanical properties of these materials is comprehensively investigated. It is demonstrated that, with respect to their intrinsic brittleness/ductile nature, all these materials exhibit ubiquitous pressure-enhanced ductility. By analyzing the strength variation under uniform deformation, together with the corresponding electronic structures, we reveal for the first time that the pressure-induced mechanical softening/weakening exhibits distinct characteristics between diamond and c-BN, owing to the differences in their abnormal charge-depletion evolution under applied strain, whereas a monotonous weakening phenomenon is observed in Si and Ge. Further investigation into dislocation-mediated plastic resistance indicates that the pressure-induced shuffle-set plane softening in diamond (c-BN), and weakening in Si (Ge), can be attributed to the reduction of antibonding states below the Fermi level, and an enhanced metallization, corresponding to the weakening of the bonds around the slipped plane with increasing pressure, respectively. These findings not only reveal the physical mechanism of pressure-induced softening/weakening in covalent materials, but also highlights the necessity of exploring strain-tunable electronic structures to emphasize the mechanical response in such covalent materials.
收稿日期: 2021-01-19
出版日期: 2021-05-02
引用本文:
. [J]. 中国物理快报, 2021, 38(5): 56101-.
Tengfei Xu, Shihao Zhang, Dominik Legut, Stan Veprek, and Ruifeng Zhang. Revealing the Pressure-Induced Softening/Weakening Mechanism in Representative Covalent Materials. Chin. Phys. Lett., 2021, 38(5): 56101-.
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2021, Vol. 38 
