Elastic Anisotropic and Thermodynamic Properties of Two BC_{7} 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-BC_{7} and Pmm2-BC_{7} have been studied in this paper utilizing first-principles calculations. In comparison with the elastic properties of Pmm2-BC_{7}, P3m1-BC_{7} 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-BC_{7} 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 BC_{7} then demonstrate that Pmm2-BC_{7} exhibits a larger elastic anisotropy than P3m1-BC_{7}. Quasi-harmonic Debye model is finally applied to investigate the Debye temperature, the coefficient of thermal expansion, heat capacity and Grüneisen parameter of Pmm2-BC_{7} and P3m1-BC_{7}. |

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