Abstract A new type of ternary monocarbides M0.5Re0.5C (M = V, Nb, Ta) with outstanding mechanical properties were firstly reported by introducing the Re into their well-known hard parent compounds MC to tune the valence electron concentration (VEC). By an efficient structure searching method, a universal orthorhombic structure with space group of Cmc21 has been uncovered and demonstrated to be the ground-state phase of these three monocarbides, which can be sustained up to the ultrahigh pressure of 300 GPa for V0.5Re0.5C and Nb0.5Re0.5C. The thermodynamic and dynamical stabilities of the predicted phases were confirmed by the formation enthalpy and phonon spectra calculations. The structural, mechanical as well as electronic properties of M0.5Re0.5C in comparison with their parent compounds MC were thus fully investigated using first-principles density functional theory (DFT) calculations. Compared to their parent compounds MC, results on the mechanical calculations indicated that they not only possess larger Vickers hardness and ideal indentation shear strength values but also exhibit much smaller elastic and ideal strength anisotropy which are advantageous to their potential applications. Detailed analysis of electronic structures reveals that the origin of the improved mechanical properties of M0.5Re0.5C is mainly attributed to the enhanced hybridization of metals-d and C-2p orbitals by locating the fermi level at the valley of the pseudogap.

中文翻译：

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基于第一性原理计算的新型斜方晶系三元碳化物M0.5Re0.5C (M=V, Nb, Ta)的理论研究

摘要 首次报道了一种新型三元单碳化物 M0.5Re0.5C (M = V, Nb, Ta)，通过将 Re 引入其众所周知的硬母体化合物 MC 以调节价电子浓度 (VEC)，具有优异的机械性能。 . 通过有效的结构搜索方法，发现了空间群为 Cmc21 的通用正交结构，并证明它是这三种单碳化物的基态相，它可以承受高达 300 GPa 的超高压 V0.5Re0。 5C 和 Nb0.5Re0.5C。通过形成焓和声子光谱计算证实了预测相的热力学和动力学稳定性。M0.5Re0 的结构、机械和电子特性。因此，使用第一性原理密度泛函理论 (DFT) 计算充分研究了 5C 与其母体化合物 MC 的比较。与其母体 MC 相比，力学计算结果表明，它们不仅具有更大的维氏硬度和理想的压痕剪切强度值，而且还表现出更小的弹性和理想的强度各向异性，这有利于其潜在应用。对电子结构的详细分析表明，M0.5Re0.5C 机械性能改善的原因主要是通过将费米能级定位在赝隙谷来增强金属-d 和 C-2p 轨道的杂化。力学计算结果表明，它们不仅具有较大的维氏硬度和理想的压痕剪切强度值，而且还表现出更小的弹性和理想的强度各向异性，这有利于其潜在应用。对电子结构的详细分析表明，M0.5Re0.5C 机械性能改善的原因主要是通过将费米能级定位在赝隙谷来增强金属-d 和 C-2p 轨道的杂化。力学计算结果表明，它们不仅具有较大的维氏硬度和理想的压痕剪切强度值，而且还表现出更小的弹性和理想的强度各向异性，这有利于它们的潜在应用。对电子结构的详细分析表明，M0.5Re0.5C 机械性能改善的原因主要是通过将费米能级定位在赝隙谷来增强金属-d 和 C-2p 轨道的杂化。