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The effect of structure and phase transformation on the mechanical properties of Re2N and the stability of Mn2N

Authors

  • Xiang Po Du,

    1. Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China
    2. Department of Physics, Institute for Computational Materials Science, Henan University, Kaifeng 475004, People's Republic of China
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  • Veng Cheong Lo,

    Corresponding author
    1. Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China
    • Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China
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  • Yuan Xu Wang

    Corresponding author
    1. Department of Physics, Institute for Computational Materials Science, Henan University, Kaifeng 475004, People's Republic of China
    • Department of Physics, Institute for Computational Materials Science, Henan University, Kaifeng 475004, People's Republic of China
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Abstract

First-principles calculations were carried out on recently synthesized Re2 and Re3 as well as hypothetical Tc and Mn nitrides. It is found that structure and covalent bonds play an important role in determining mechanical properties. Under a large strain along (0001)〈1010〉direction, Re2N undergoes a phase transformation with a slight increase in ideal shear strength. On the other hand, it is transformed into a phase with weaker mechanical properties, if the strain is along Re21210〉 direction. Mn2N can be synthesized under moderate conditions due to its more negative formation energy. Re2N, Re3N, and Mn2N show structure-related mechanical property under larger strains to ReB2 but exhibit much lower ideal strengths, which is attributed to the larger ionicity of cation–anion bond. Three-dimensional framework of strong covalent bonds is thus highly recommended to design superhard materials. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011

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