Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂BS/∂P = 3.81(3) and ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions.

中文翻译：

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六方结构的ε-NbN：超压缩性，高剪切刚度和可能的硬超导材料。

探索六角形ε-NbN的结构稳定性和弹性有助于发现其物理性质之间的相关性，以供科学和技术应用。在这里，我们首次使用超声干涉法和原位X射线衍射测量了多晶六角形ε-NbN的超压缩性和高剪切刚度，并辅以第一原理密度函数理论计算，压力高达30 GPa 。使用状态的有限应变方程式，可从测得的速度和密度得出弹性体积和剪切模量以及它们的压力依赖性，得出BS0 = 373.3（15）GPa，G0 = 200.5（8）GPa，∂BS /∂P= 3.81（3）和∂G/∂P= 1.67（1）。六角形的ε-NbN具有非常高的体积模量，可与超硬材料cBN的体积模量相媲美（B0 = 381.1 GPa）。高剪切刚度可与超硬γ-B（G0 = 227.2 GPa）相媲美。我们发现过渡金属氮化物的晶体结构和相应金属的最外电子可能在体积模量和剪切模量方面主导着它们的压力依赖性。此外，弹性模量，维氏硬度，德拜温度，熔化温度以及六方ε-NbN的可能超导性都随压力而增加，这表明其在极端条件下的应用非常适合。