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First-Principles Study of the Nonlinear Elasticity of Rare-Earth Hexaborides REB6 (RE = La, Ce)

1
School of Mathematical Sciences and Physics, Jinggangshan University, Ji’an 343009, China
2
Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
3
School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China
4
School of Materials Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China
*
Author to whom correspondence should be addressed.
Academic Editor: Helmut Cölfen
Crystals 2017, 7(11), 320; https://doi.org/10.3390/cryst7110320
Received: 30 March 2017 / Revised: 16 October 2017 / Accepted: 20 October 2017 / Published: 25 October 2017
The complete set of independent second- and third-order elastic constants of rare-earth hexaborides LaB 6 and CeB 6 are determined by the combination method of first-principles calculations and homogeneous deformation theory. The ground-state lattice parameters, second-order elastic constants, and bulk modulus are in reasonable agreement with the available experimental data. The third-order elastic constant of longitudinal mode C 111 has a larger absolute value than other shear modes, showing the contribution to lattice vibrations from longitudinal modes to be greater. The pressure derivatives of the second-order elastic constants related to the third-order elastic constants are calculated to be positive for the two hexaborides, which are consistent with those of their polycrystalline bulk modulus and shear modulus. Furthermore, the effect of pressure on the structural stability, mechanical property, and elastic anisotropy of the two hexaborides are investigated, showing a reduction in mechanical stability and an increase in ductility and anisotropy with increasing pressure. View Full-Text
Keywords: rare-earth hexaborides; elastic constants; mechanical property; elastic anisotropy; first-principles rare-earth hexaborides; elastic constants; mechanical property; elastic anisotropy; first-principles
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Zeng, X.; Ye, Y.; Zou, S.; Gou, Q.; Wen, Y.; Ou, P. First-Principles Study of the Nonlinear Elasticity of Rare-Earth Hexaborides REB6 (RE = La, Ce). Crystals 2017, 7, 320.

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