First-principles prediction on the high-pressure structures of transition metal diborides (TMB2, TM = Sc, Ti, Y, Zr).
First-principles prediction on the high-pressure structures of transition metal diborides (TMB2, TM = Sc, Ti, Y, Zr).
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DOI：
10.1021/ic100214v
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发表时间：
2010-06
影响因子：
4.6
通讯作者：
Meiguang Zhang;Hui Wang;Hongbo Wang;Xinxin Zhang;T. Iitaka;Yanming Ma
中科院分区：
文献类型：
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作者：
Meiguang Zhang;Hui Wang;Hongbo Wang;Xinxin Zhang;T. Iitaka;Yanming Ma
利用第一性原理结构预测方法，我们对常压下AlB（2）型结构稳定的过渡金属二硼化物（TMB（2），TM = Sc，Ti，Y，Zr）的高压结构进行了广泛的研究。我们发现了两种新的高压结构：（i）ScB（2）和YB（2）的单斜结构（C2/m，Z = 4）分别稳定在208和163 GPa以上;（ii）TiB（2）的四相α-ThSi（2）型相（I4（1）/amd，Z = 4）稳定在215 GPa以上。计算结果表明，压力下过渡金属TM向B的电子转移可能是导致结构相变的主要原因。进一步的声子和硬度计算表明，TiB（2）中的α-ThSi（2）相可在常压下淬火，并具有优异的力学性能，维氏硬度为29.8GPa。有趣的是，ZrB（2）是相当稳定的，并且在高达至少300 GPa的环境压力下保持AlB（2）型结构。我们将过渡金属Zr和B之间的强共价杂化归因于这种超稳定性。
We have extensively explored the high-pressure structures of transition-metal diborides (TMB(2), TM = Sc, Ti, Y, and Zr) stabilized with the AlB(2)-type structure at ambient pressure by using first-principles structural prediction. We find two novel high-pressure structures: (i) a monoclinic structure (C2/m, Z = 4) for ScB(2) and YB(2) stable above 208 and 163 GPa, respectively; and (ii) a tetragonal alpha-ThSi(2)-type phase (I4(1)/amd, Z = 4) for TiB(2) stable above 215 GPa. Our calculations show that the electron transfer from transition-metals TM to B under pressure might be the main cause for the structural phase transitions. Further phonon and hardness calculations suggest that alpha-ThSi(2) phase of TiB(2) is quenchable to ambient pressure and possesses excellent mechanical property with a Vickers hardness of 29.8 GPa. Interestingly, ZrB(2) is quite stable and persists on the ambient-pressure AlB(2)-type structure up to at least 300 GPa. We attribute the strong covalent hybridization between the transition-metal Zr and B to this ultrastability.