Yu Rongmei, Sun Ermiao, Jiao Liguang, Cai Yongmao, Wang Hongbo, Yao Yansun
State Key Laboratory of Superhard Materials, College of Physics, Jilin University Changchun 130012 P. R. China
College of Physics and Electronic Engineering, Nanyang Normal University Nanyang 473061 P. R. China.
RSC Adv. 2018 Oct 26;8(64):36412-36421. doi: 10.1039/c8ra07814a.
We have extensively explored the stable crystal structures of early-transition metal pernitrides (TMN, TM = Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, and Ta) at ambient and high pressures using effective CALYPSO global structure search algorithm in combination with first-principles calculations. We identified for the first time the ground-state structures of MnN, TaN, NbN, VN, ZrN, and HfN pernitrides, and proposed their synthesis pressures. All predicted crystal structures contain encapsulated N dumbbells in which the two N atoms are singly bonded to a [N] pernitride unit utilizing the electrons transferred from the transition metals. The strong nature of the single dinitrogen bond and transition metal-nitrogen charge transfer induce extraordinary mechanic properties in the predicted transition metal pernitrides including large bulk modulus and high Vickers hardness. Among the predictions the hardness of MnN is 36.6 GPa, suggesting that it is potentially a hard material. The results obtained in the present study are important to the understanding of structure-property relationships in transition metal pernitrides and will hopefully encourage future synthesis of these technologically important materials.
我们使用有效的CALYPSO全局结构搜索算法结合第一性原理计算，广泛探索了早期过渡金属过氮化物（TMN，TM = Ti、V、Cr、Mn、Zr、Nb、Mo、Hf和Ta）在常压和高压下的稳定晶体结构。我们首次确定了MnN、TaN、NbN、VN、ZrN和HfN过氮化物的基态结构，并提出了它们的合成压力。所有预测的晶体结构都包含封装的N哑铃结构，其中两个N原子利用从过渡金属转移的电子与一个[N]过氮化物单元单键相连。单二氮键的强性质和过渡金属-氮电荷转移在预测的过渡金属过氮化物中诱导出非凡的力学性能，包括大的体积模量和高的维氏硬度。在这些预测中，MnN的硬度为36.6 GPa，表明它可能是一种硬质材料。本研究获得的结果对于理解过渡金属过氮化物中的结构-性能关系很重要，并有望促进未来对这些具有重要技术意义的材料的合成。
