Unexpectedly low indentation strength of WB3 and MoB3 from first principles
Unexpectedly low indentation strength of WB3 and MoB3 from first principles
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根据第一原理，WB3 和 MoB3 的压痕强度出乎意料地低
DOI：
10.1103/physrevb.86.180101
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发表时间：
2012-11
影响因子：
3.7
通讯作者：
Chen, Changfeng
中科院分区：
文献类型：
--
作者：
Zang, Chenpeng;Sun, Hong;Chen, Changfeng
近年来，合成的WB因其在过渡金属轻元素化合物中具有最高的显微硬度而引起人们极大的兴趣。最新的理论研究[见，例如，Zhang等人，物理修订信函108，255502（2012）10.1103/PhysRevLett.108.255502]显示，然而，先前指定的WB结构是不稳定的; WB结构被提出作为替代结构模型。在这里，我们显示的第一原理计算，压头下的压力驱动器的横向债券和体积膨胀，在拟议的WBand相关的MoB结构，导致意外的低压痕强度的水平远低于ReB。这与实验结果直接矛盾，实验结果表明WB具有比ReB更高的压痕硬度。此外，计算出的WB（和MoB）的归一化比率表现出负压力依赖性，这与实验观察到的趋势不一致。因此，我们的结论是，拟议的WB结构与实验结果是不相容的，合成（标称）WB的晶体结构的问题必须重新开放作进一步研究。
Recently, synthesized WBhas attracted great interest because it exhibits the highest microindentation hardness among transition-metal light-element compounds. The latest theoretical studies [see, e.g., Zhanget al., Phys. Rev. Lett. 108, 255502 (2012)10.1103/PhysRevLett.108.255502] show, however, that the previously assigned WBstructure is unstable; a WBstructure was proposed as an alternative structural model. Here we show by first-principles calculations that the pressure beneath the indenter drives a lateral bond and volume expansion in the proposed WBand related MoBstructures, resulting in an unexpectedly low indentation strength to a level well below that of ReB. This is in direct contradiction to experimental results that show WBhas higher indentation hardness compared to ReB. Moreover, the calculated normalizedratio of WB(and MoB) exhibits a negative pressure dependence, which is inconsistent with the experimentally observed trend. We therefore conclude that the proposed WBstructure is incompatible with experimental results and that the question of the crystal structure of the synthesized (nominal) WBmust be reopened for further study.