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 $\mathrm{hP}6\text{−}{\mathrm{WN}}_2$, 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.

中文翻译：

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非同寻常的压痕应变强化产生超硬氮化钨

过渡金属轻质化合物是为新一代超硬固体量身定制的一类设计材料，但压痕应变软化迄今将其固有的不变载荷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，我们报告从第一性原理计算得出的结果，即两种氮化钨hP4-WN和$\mathrm{生命值}6\text{-}{\mathrm{WN}}_{\mathrm{2个}}$表现出非凡的应变刚度，产生超过40 GPa的压痕强度，从而大大提高了人们寻求长期寻求的非传统超硬固体的前景。计算表明，hP4-WN在平衡状态和压痕状态下均为金属，这使其成为第一种已知的本征超硬金属。X射线衍射图谱分析表明在最近合成的样品中存在hP4-WN。我们阐明了用于确定的结构加固的复杂结合和应力响应机制，这些见解可能有助于推进合理设计和发现其他新型超硬材料的过程。