超硬过渡金属硼化物的结构和硬度微观机理的理论研究

Transition metal borides are regarded as the most promising candidates of superhard materials. This interest of designing newly superhard materials is motivated by the technological requirement and need for physically and chemically resistant materials for cutting tools and wear coatings, overcoming the technological limits of applicability of diamond and cubic boron nitride, used for processing and polishing of iron-based alloys. This is reflected in the variety of scientific problems that are the focus of the intersection between and atomic and molecular physics and condensed matter physics. The understanding of the micromechanism of hardness is a typical example of physical problems. .The objective of this project is to study the structural features, phase stability and hardness of transition metal (Cr, Mn, Fe) borides TMBn (n=2-4). It concretely aims at the key scientific problems regarding the design and synthesis of the novel superhard materials. Using the particle swarm optimization technique on crystal structure coupling method combing with the first principles calculations, the main research content of this project includes three aspects as follow: 1) the structural features of superhard transition metal borides; 2) the phase stability of the predicted structure and the corresponding pressure-induced structural transition sequences; 3) the potential superhard behavior of transition metal borides and the main influence factors of the hardness micromechanism. This research is not only to explore the structural features and phase stability of transition metal borides which have been not synthesized at present experiment, but also provides valuable theoretical basis on understanding the micromechanism of hardness and superhard behavior of transition metal light element compound. It has important scientific significance in the development of the cross field between atomic and molecular physics and condensed matter physics.

本项目以超硬过渡金属（Cr，Mn, Fe）硼化物TMBn (n=2-4)为研究对象，具体针对超硬过渡金属硼化物的结构特征和影响硬度的微观机理这一关键性科学问题展开研究。本项目拟采用基于粒子群优化算法的晶体结构预测方法和基于密度泛函理论的第一性原理计算。研究内容包括：超硬过渡金属（Cr，Mn, Fe）硼化物TMBn (n=2-4)的结构特征；预测结构的相稳定性、高压下的相变序列和可能的合成路径；过渡金属硼化物的超硬性和影响硬度的微观机理。本项目不仅为探明目前实验尚未合成的过渡金属硼化物的结构特征和相稳定性提供可能的理论参考，而且还为理解影响过渡金属硼化物硬度的微观机理提供有价值的理论依据，为探寻新型超硬材料指明方向，这对推动原子分子物理和凝聚态物理的交叉发展具有重要的科学意义。

新型超硬材料的设计和合成是当今凝聚态物理、原子分子物理、材料科学等交叉领域研究的热点课题之一。项目采用基于粒子群优化算法的晶体预测方法和基于密度泛函的第一性原理计算方法重点研究了超硬过渡金属（Cr, Mn, Fe）硼化物TMBn (n=2-4)的结构特征和电子性质，并探索影响其硬度的微观机理。主要研究内容为超硬过渡金属（Cr, Mn, Fe）硼化物TMBn (n=2-4)的结构特征；相稳定性、高压下的相变序列和可能的合成路径；揭示了硼化物的多功能性（超级不可压缩性、高热容、高熔点、半导体性）、超硬性和影响硬度的微观机理。此外，本项目执行期间还利用相同的研究方法基于密度泛函的第一性原理计算方法研究了其他的新型功能材料。取得的主要研究成果如下：1）BnXn、CBn-1Xn和C10X8中配体对稳定性的影响及其在锂离子电池电解液的潜在应用；利用配体效应改良了一种离子液体电解液；2）平面四配位原子嵌入石墨烯纳米带进行磁性调节；3）Al-Li双金属合金纳米结构的储氢性质。本项目的研究成果将为探寻新型超硬材料和无卤素安全的金属离子电池提供一些理论参考。在本项目资助下发表学术论文8篇，全部被SCI收录。