Extraordinary Indentation Strain Stiffening Produces Superhard Tungsten Nitrides
Extraordinary Indentation Strain Stiffening Produces Superhard Tungsten Nitrides
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非凡的压痕应变强化产生超硬氮化钨
DOI：
10.1103/physrevlett.119.115503
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发表时间：
2017-09-15
影响因子：
8.6
通讯作者：
Chen, Changfeng
中科院分区：
文献类型：
--
作者：
Lu, Cheng;Li, Quan;Chen, Changfeng
过渡金属轻元素化合物是一类专为成为新一代超硬固体而设计的材料，但压痕应变软化迄今为止将其固有的载荷不变硬度限制在远低于通常为超硬材料设定的40 GPa阈值。在这里，我们报告的结果从第一原理计算，两个氮化钨，hP4-WN和hP 6-WN 2，表现出非凡的应变硬化，产生显着增强的压痕强度超过40 GPa，提高了令人兴奋的前景，实现长期寻求的非传统超硬固体。计算表明，hP4-WN在平衡和压痕下都是金属，标志着它是第一个已知的本征超硬金属。X-射线衍射图分析表明在最近合成的样品中存在hP4-WN。我们阐明了复杂的键合和应力响应机制，确定的结构强化，和见解可能有助于推进合理的设计和发现额外的新型超硬材料。
Transition-metal light-element compounds are a class of designer materials tailored to be a new generation of superhard solids, but indentation strain softening has hitherto limited their intrinsic load-invariant hardness to well below the 40 GPa threshold commonly set for superhard materials. Here we report findings from first-principles calculations that two tungsten nitrides, hP4-WN and hP6-WN2, exhibit extraordinary strain stiffening that produces remarkably enhanced indentation strengths exceeding 40 GPa, raising exciting prospects of realizing the long-sought nontraditional superhard solids. Calculations show that hP4-WN is metallic both at equilibrium and under indentation, marking it as the first known intrinsic superhard metal. An x-ray diffraction pattern analysis indicates the presence of hP4-WN in a recently synthesized specimen. We elucidate the intricate bonding and stress response mechanisms for the identified structural strengthening, and the insights may help advance rational design and discovery of additional novel superhard materials.