过渡金属化合物作为新型超硬材料，克服了金刚石等常见超硬材料的固有缺陷，正以其耐热性高、化学惰性好、成本相对低廉等优势成为多功能材料研究的前沿热点。本项目突破了长期追求高电子浓度的高体模量设计思路，创新性提出从能量角度评估过渡金属化合物体系的热力学稳定性，寻找具有立体共价网络的多种热力学稳定相进行超硬微纳尺度设计，具有新颖性。以多相过渡金属硼化物MBx(M=Cr、Mn和Fe)为重点研究对象，探索它们热力学稳定性与力学特性及其变化规律；阐明热力学稳定的高硬度相的物理起源；建立过渡金属化合物超硬微纳尺度设计准则；进而进行新超硬相设计、样品制备与性能表征。本项目采用模拟计算、理论分析与实验制备相结合的方法，开展材料、物理与力学等多学科交叉研究，有望获得全新的超硬设计准则，为设计新型超硬材料提供理论依据；并有可能制备出多功能耦合的超硬相，它们在海洋工程等领域应用潜力巨大。

Transition-metal compounds are a new type of superhard materials that overcome intrinsic limitations of conventional superhard materials such as diamond. They possess some advantages of high heat resistance, good chemical intertness, and relatively low cost, and thus become the frontier research hotspot of multifunctional materials. In present project, the thermodynamic stability of transition-metal compounds will be evaluated from the energy idea, and microscale and nanoscale design of superhardness will be performed on basis of the thermodynamically stable phases with the three-dimensional covalent network. This creative proposal breaks through the design idea of high bulk modulus based on long-pursuing high electron concentration. Using multiphase metal borides MBx (M=Cr, Mn and Fe) as representative cases, the thermodynamic stability, mechanical properties, and their change regularities will be systematically explored. The physical origins of thermodynamic and superhard phases will be revealed. The microscale and nanoscale design criterion of superhardness of transition-metal compounds will be established. The design of new superhard phases will be performed, their samples will be synthesized and their multiple functionalities will be characterized. In this project, the combination of simulation calculations, theoretical analyses with experimental preparations will be adopted to perform the multi-disciplinary investigation (e.g., material, physics and mechanics). A new superhard design criterion promises to be established, which provides a theoretical guidance for designing new superhard materials. Moreover, new superhard phases with multiple functionalities may be obtained and have high potential applications in many fields such as ocean engineerings.