Phase Stability, Physical Properties, and Hardness of Transition-Metal Diborides MB2 (M = Tc, W, Re, and Os): First-Principles Investigations

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• 作者：Ming-Min Zhong ; Xiao-Yu Kuang ; Zhen-Hua Wang ; Peng Shao ; Li-Ping Ding ; Xiao-Fen Huang
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：May 23, 2013
• 年：2013
• 卷：117
• 期：20
• 页码：10643-10652
• 全文大小：501K
• 年卷期：v.117,no.20(May 23, 2013)
• ISSN：1932-7455

文摘

Using first-principles calculations, the structural stability, elastic strength, and formation enthalpies of four diborides MB₂ (M = Tc, W, Re, and Os) are investigated by means of the pseudopotential plane-waves method, as well as the roles of covalency and bond topology in the phase incompressibility. Three candidate structures of known transition-metal diborides are chosen to probe. The calculated lattice parameters, elastic properties, Poisson鈥檚 ratio, and B/G ratio are derived. It is observed that the ReB₂-type structure containing well-defined zigzag covalent chains exhibits an unusual incompressibility along the c axis comparable to that of diamond. Formation enthalpy calculations demonstrate that the ground-state phase is synthesizable at low pressure, whereas the other phase can be achieved through the phase transformation. Moreover, according to Mulliken overlap population analysis, a semiempirical method to evaluate the hardness of multicomponent crystals with a partial metallic bond is presented. The predicted hardness of WB₂鈥揥B₂, ReB₂鈥揜eB₂, and OsB₂鈥揙sB₂ is in reasonable agreement with experiment data. Both strong covalency and a zigzag topology of interconnected bonds underlie the ultraincompressibilities. In addition, the superior performance and largest hardness of ReB₂鈥揜eB₂ indicate that it is a superhard material. This work provides a useful guide for designing novel borides materials having excellent mechanical performances.