Experimental and Computational Studies on Superhard Material Rhenium Diboride under Ultrahigh Pressures
Experimental and Computational Studies on Superhard Material Rhenium Diboride under Ultrahigh Pressures
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DOI：
10.3390/ma13071657
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发表时间：
2020-04-01
期刊：
影响因子：
3.4
通讯作者：
Vohra, Yogesh K.
中科院分区：
文献类型：
--
作者：
Burrage, Kaleb C.;Lin, Chia-Min;Vohra, Yogesh K.
用于极端环境应用的一类新兴超硬材料是由重过渡金属与轻元素形成的化合物。在这项工作中，在等温和非静水压条件下，在金刚石砧室中进行了过渡金属二硼化铼（ReB2）的超高压实验。首次在 ReB2 上进行了两次独立的高压实验，压力高达 241 GPa（体积压缩 V/V-0 = 0.731 +/- 0.004），并以铂作为 X 射线衍射研究中的内压标准。 ReB2的六方相在最高压力下是稳定的，并且a轴和c轴压缩之间的各向异性随着压力增加至241 GPa。 ReB2 屈服应力之上的测量状态方程 (EOS) 可以用体积模量 K-0 = 364 GPa 及其一阶压力导数 K-0 ' = 3.53 很好地表示。 EOS 和弹性常数的相应密度泛函理论 (DFT) 模拟与实验数据非常吻合。 DFT 结果表明，ReB2 变得更具延展性，在压缩下金属结合的趋势增强。 DFT 结果还显示出在所研究的最大压力下晶体具有很强的各向异性。沿 Re 和 B 键方向的压力增强电子密度分布使材料沿 c 轴高度不可压缩。我们的研究有助于为ReB2在超高压下的各向异性压缩奠定基础。
An emerging class of superhard materials for extreme environment applications are compounds formed by heavy transition metals with light elements. In this work, ultrahigh pressure experiments on transition metal rhenium diboride (ReB2) were carried out in a diamond anvil cell under isothermal and non-hydrostatic compression. Two independent high-pressure experiments were carried out on ReB2 for the first time up to a pressure of 241 GPa (volume compression V/V-0 = 0.731 +/- 0.004), with platinum as an internal pressure standard in X-ray diffraction studies. The hexagonal phase of ReB2 was stable under highest pressure, and the anisotropy between the a-axis and c-axis compression increases with pressure to 241 GPa. The measured equation of state (EOS) above the yield stress of ReB2 is well represented by the bulk modulus K-0 = 364 GPa and its first pressure derivative K-0 ' = 3.53. Corresponding density-functional-theory (DFT) simulations of the EOS and elastic constants agreed well with the experimental data. DFT results indicated that ReB2 becomes more ductile with enhanced tendency towards metallic bonding under compression. The DFT results also showed strong crystal anisotropy up to the maximum pressure under study. The pressure-enhanced electron density distribution along the Re and B bond direction renders the material highly incompressible along the c-axis. Our study helps to establish the fundamental basis for anisotropic compression of ReB2 under ultrahigh pressures.