硼化钛结构稳定性、力学和热力学性能理论研究

Theoretical Study on the Stabilities, Mechanical and Thermal Properties

摘要:

采用基于第一性原理的密度泛函理论计算了硼化钛的稳定性、电子结构、弹性模量、各项异性参数和低温热容等。计算结果表明，硼化钛的成键包含金属、共价和离子键，Ti2B的金属性最强，而TiB2的共价性最明显；其中TiB_与TiB_分别为热力学与力学失稳结构，而TiB2的稳定性最佳，TiB2的体模量、剪切模量和杨氏模量分别为251.4，260.1和564.6 GPa，显著高于其他硼化钛。B/G值表明，TiB2的韧性差，从而限制了其作为切削工具或耐磨部件的应用。因此，认为要获得良好的韧性与耐磨性，应设计制备TiB2基复合材料

Abstract:

The stability, electronic structure, elasticity, and heat capacity of titanium borides were calculated by first-principles density functional theory. The results show that TiB with the space group of and are unstable, and the most stable stucture belongs to TiB2. All of the borides show a mixed character of metallic, covalent and ionic bonds, Ti2B shows high metallic property, while TiB2 has high level of covalent bonding. The values of bulk moduli, shear moduli and Young’s moduli are 251.4, 260.1 and 564.6 GPa, respectively, which are obviously higher than that of other borides. The calculated B/G values clearly imply that TiB2 is more brittle than other borides. The brittle nature of TiB2 (B/G=0.97) constrains its application as potential cutting tools or wear resistant parts. Thus TiB2-based composites should be designed in order to improve the ductile property. Finally, the anisotropy index and heat capacity of the titanium borides were also predicted