Elastic Anisotropic and Thermodynamic Properties of Two BC7 Phases
Mengjiang Xing, Binhua Li, Zhengtao Yu and Qi Chen
Faculty of Information Engineering and Automation, Kunming University of Science and Technology, Kunming, 650051, PR China
Received: December 25, 2016; In final form: June 21, 2017
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The structural, elastic, anisotropic, and thermodynamic properties of P3m1-BC7 and Pmm2-BC7 have been studied in this paper utilizing first-principles calculations. In comparison with the elastic properties of Pmm2-BC7, P3m1-BC7 exhibits slightly higher values in bulk modulus and B/G, with similar values in shear modulus, the Young modulus, and the Poisson ratio. The calculated Pugh modulus ratio (B/G) and the Poisson ratio demonstrates P3m1-BC7 from brittle to ductile at 93.60 and 93.73 GPa, respectively. Calculations of shear anisotropic factor, universal elastic anisotropy index, shear modulus, the Young modulus, and the Poisson ratio for BC7 then demonstrate that Pmm2-BC7 exhibits a larger elastic anisotropy than P3m1-BC7. Quasi-harmonic Debye model is finally applied to investigate the Debye temperature, the coefficient of thermal expansion, heat capacity and Gr√ľneisen parameter of Pmm2-BC7 and P3m1-BC7.

DOI: 10.12693/APhysPolA.132.1340
topics: ab initio calculations, elastic properties, anisotropic properties, thermodynamic properties