Stability and elastic properties of NbxCy compounds

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...

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Bibliographic Details
Published in中国物理B：英文版 no. 9; pp. 466 - 473
Main Author 高旭鹏 蒋业华 刘洋赈 周荣 冯晶
Format Journal Article
LanguageEnglish
Published 01.09.2014
Subjects
体积弹性模量
化合物
各向异性指数
密度泛函理论
弹性性质
机械性能
杨氏模量
稳定性
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ISSN1674-1056
2058-3834
DOI10.1088/1674-1056/23/9/097704

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Summary: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 （A^U）, 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.
Bibliography: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 （A^U）, 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.
11-5639/O4
ceramic, carbides, anisotropy, hardness
Gao Xu-Peng, Jiang Ye-Hua, Liu Yang-Zhen, Zhou Rong, Feng Jing（1. Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China; 2. School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA）
ISSN:1674-1056
2058-3834
DOI:10.1088/1674-1056/23/9/097704