First-principles study of structure and mechanical properties of TMB 12 (TM = W and Ti) superhard material under pressur
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First-principles study of structure and mechanical properties of TMB12(TM = W and Ti) superhard material under pressure Yong Pan1,a)
Yanlin Jia2,b)
1
School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, China College of Materials Science and Engineering, Central South University, Changsha 410083, China; and College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China a) Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] 2
Received: 26 July 2019; accepted: 20 August 2019
We apply the first-principles calculations to investigate the structure, mechanical, and thermodynamic properties of WB12 and TiB12 under high pressure (0–100 GPa). The calculated results show that WB12 and TiB12 are thermodynamically stable at the 0 GPa or high pressure. WB12 is more thermodynamically stable than TiB12. In particular, the calculated Vickers hardness of WB12 and TiB12 at the ground state is 29.9 GPa and 43.2 GPa, respectively, indicating that TiB12 is a potential superhard material. With increasing pressure, the calculated elastic modulus of WB12 and TiB12 increases gradually. The calculated electronic structure shows that the high Vickers hardness and elastic properties of WB12 and TiB12 derive from the 3D network B–B covalent bonds. In addition, the calculated Debye temperature at the ground state is 927 K for WB12 and 1339 K for TiB12, respectively. With increasing pressure, the calculated Debye temperature of WB12 and TiB12 increases gradually. Our work shows that TiB12 not only exhibits high hardness but also shows better thermodynamic properties in comparison with WB12.
Introduction Transition metal borides (TMBs) have received great interest due to the high hardness, high strength, excellent thermal stability, and high melting point, etc. [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. The previous works have shown that the measured or calculated Vickers hardness of ReB2, CrB4, and WB4 is up to 50.3 GPa [11], 43–49 GPa [12], and 41.1 GPa [13], respectively, which are regarded as the potential new-generation superhard materials. In addition to the high hardness, compared to the diamond, those TMBs superhard materials not only show excellent electronic properties but also exhibit good thermodynamic properties under high temperature [14, 15, 16, 17, 18]. The first-principles calculations have shown that the high hardness of TMBs is attributed to the formation of B–B covalent bond and TM–B bond [19, 20, 21]. In particular, the boron concentration plays a crucial role in the mechanical properties of TMBs superhard materials. Therefore, the boron-rich region borides have attracted growing interest in recent years [22, 23].
ª Materials Research Society 2019
Among those TMBs, transition metal dodecaborides (TMB12) show prominent mechanical properties due to the high concentration of boron and the 3D network B–B covalent bonds. As the potential superhard materials, ZrB12 and HfB12 have been widely investigated over t
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