›› 2014, Vol. 23 ›› Issue (9): 97704-097704.doi: 10.1088/1674-1056/23/9/097704

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

Stability and elastic properties of NbxCy compounds

高旭鹏a, 蒋业华a, 刘洋赈a, 周荣a, 冯晶b   

  1. a Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China;
    b School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
  • 收稿日期:2013-11-13 修回日期:2014-01-14 出版日期:2014-09-15 发布日期:2014-09-15
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 51171074 and 51261013).

Stability and elastic properties of NbxCy compounds

Gao Xu-Peng (高旭鹏)a, Jiang Ye-Hua (蒋业华)a, Liu Yang-Zhen (刘洋赈)a, Zhou Rong (周荣)a, Feng Jing (冯晶)b   

  1. a Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China;
    b School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
  • Received:2013-11-13 Revised:2014-01-14 Online:2014-09-15 Published:2014-09-15
  • Contact: Jiang Ye-Hua E-mail:jiangyehua@kmust.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 51171074 and 51261013).

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摘要： Density functional theory (DFT) is applied to investigate the stability and mechanical properties of NbxCy compounds. The structures of NbxCy compounds are optimized, and the results are in good agreement with previous work. The calculated results of the cohesive energy and the formation enthalpy of NbxCy show that they are thermodynamically stable structures, except for Pmc21-Nb2C. The mechanical properties such as the bulk modulus, Young's modulus, the shear modulus, and Poisson's ratio are obtained by Voigt-Reuss-Hill approximation. The results show that the Young's modulus and shear modulus of NbC are larger than other NbxCy compounds. The mechanical anisotropy is characterized by calculating several different anisotropic indexes and factors, such as universal anisotropic index (AU), shear anisotropic factors (A1, A2, A3), and percent anisotropy (AB and AG). The surface constructions of bulk and Young's moduli are illustrated to indicate the mechanical anisotropy. The hardness of NbxCy compounds is also discussed in this paper. The estimated hardness for all NbxCy compounds is less than 20 GPa.

关键词: ceramic, carbides, anisotropy, hardness

Abstract: Density functional theory (DFT) is applied to investigate the stability and mechanical properties of NbxCy compounds. The structures of NbxCy compounds are optimized, and the results are in good agreement with previous work. The calculated results of the cohesive energy and the formation enthalpy of NbxCy show that they are thermodynamically stable structures, except for Pmc21-Nb2C. The mechanical properties such as the bulk modulus, Young's modulus, the shear modulus, and Poisson's ratio are obtained by Voigt-Reuss-Hill approximation. The results show that the Young's modulus and shear modulus of NbC are larger than other NbxCy compounds. The mechanical anisotropy is characterized by calculating several different anisotropic indexes and factors, such as universal anisotropic index (AU), shear anisotropic factors (A1, A2, A3), and percent anisotropy (AB and AG). The surface constructions of bulk and Young's moduli are illustrated to indicate the mechanical anisotropy. The hardness of NbxCy compounds is also discussed in this paper. The estimated hardness for all NbxCy compounds is less than 20 GPa.

Key words: ceramic, carbides, anisotropy, hardness

中图分类号:  (Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.)

  • 77.84.Bw
75.30.Gw (Magnetic anisotropy) 46.55.+d (Tribology and mechanical contacts) 51.35.+a (Mechanical properties; compressibility)