单轴压缩下Ti3B4的力学、电学性能及变形机制的第一性原理研究

Mechanical, electronic properties and deformation mechanisms of Ti3B4 under uniaxial compressions:a first-principles calculation

Ti3B4作为一种重要的钛硼化合物,被广泛应用于工业生产和国防军事中.但是有关Ti3B4在外载荷下的变形行为却鲜有报道,这在很大程度上限制了它的应用.本文采用基于密度泛函理论的第一性原理方法研究了Ti3B4在不同方向单轴压缩下的力学行为、电子结构以及变形机制.结果表明,在不同方向单轴压缩下,Ti3B4的变形行为表现出很强的各向异性.a轴压缩下,层内Ti-Ti键减弱使Ti3B4承载能力降低,最终层间Ti-Ti键和沿b轴B-B键断裂造成压缩应力突降;b轴压缩下,层内Ti-B键减弱和层间Ti-B键增强导致Ti3B4承载能力逐渐降低,B-B键断裂导致结构破坏;c轴压缩下,层内Ti-B键断裂和层间Ti-B键形成使结构稳定性降低.由态密度分布可知,在单轴压缩下,变形后的Ti3B4仍然呈现金属性,但是其共价性能降低.通过讨论Ti3B4在不同方向单轴压缩下的力学行为与微观变形机制可以为改善其宏观性能提供一定的理论指导.

As an important Ti-B component,Ti3B4 has been widely used in industry and military applications.However,its deformation behaviors are not clear,which greatly limits its applications.First-principles methods based on density function theory were employed to investigate the mechanical,electronic properties and deformation mechanisms of Ti3B4 under uniaxial compressions along different axis.The results show that the structure underwent a massive change under different axial compressions.Strong anisotropic of deformation behaviors in Ti3B4 was observed.The compressive strength along b-axis is the highest in Ti3B4 structure.Under a-axis compression,the interaction between intralayer Ti—Ti bonds becomes weaker as the compressive strain increases,causing the partly damage of Ti3B4.However,in this process,the structure is not destroyed and can sustain the stress continuously.After that,the interlayer Ti—Ti bonds and the intralyer B—B bonds which are along b-axis,are broken and then it causes the sudden drop in stress,implying that the Ti3B4 structure is fully destroyed.Under b-axis compression,the changes of Ti—B bonds in Ti3B4 structure lead to the decrease of stress.Similarly,the structure can sustain the stress continuously in the process.Then,the B—B bonds which are along b-axis are broken,resulting in the sudden drop in stress.Under c-axis compression,the formation of interlayer Ti—B bonds and the breakage of intralayer Ti—B bonds result in structural instability of Ti3B4.Meanwhile,the deformed Ti3B4 still exhibits a metallic feature in the crystalline state after uniaxial compressions.However,there is no noticeable pseudogap in DOS spectra for a-axis and b-axis compressions.While for c-axis compression,there still exists a pseudogap around the Fermi energy,but it moves to the lower energy.And the pseudogap becomes narrower than that of the initial structure,which means that the covalent properties of Ti3B4 are reduced after deformations.The present work provides necessary insights in understanding the mechanical behaviors and deformation mechanisms of Ti3B4,which is the basis for improving the mechanical performance of Ti3B4 at macroscale.