物理化学学报 >> 2015, Vol. 31 >> Issue (2): 253-260.doi: 10.3866/PKU.WHXB201412242

理论与计算化学 上一篇    下一篇

Al代位合金化对D88-Ti5Si3力学性能与电子结构影响的第一性原理研究

黄豪杰, 徐江   

  1. 南京航空航天大学材料科学与技术学院, 南京 210016
  • 收稿日期:2014-10-30 修回日期:2014-12-24 发布日期:2015-01-26
  • 通讯作者: 徐江 E-mail:xujiang73@nuaa.edu.cn
  • 基金资助:

    国家自然科学基金(51374130)和航空科学基金(2013ZE52058)资助项目

First-Principles Study into the Effect of Substitutional Al Alloying on the Mechanical Properties and Electronic Structure of D88-Ti5Si3

HUANG Hao-Jie, XU Jiang   

  1. School of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China
  • Received:2014-10-30 Revised:2014-12-24 Published:2015-01-26
  • Contact: XU Jiang E-mail:xujiang73@nuaa.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51374130) and Aeronautical Science Foundation of China (2013ZE52058).

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摘要：

采用基于密度泛函理论(DFT)的第一性原理赝势平面波方法, 计算了不同数量的Al 原子代位六方D88结构的Ti5Si3晶体中的Si 原子后的形成能(ΔHf)、结合能(ΔEcoh)、体模量(B)、剪切模量(G)、泊松比(ν)、Cauchy 压力参数(C12―C66,C13―C44)、金属性(fm)和派-纳力(τP-N)等参数, 表征了Al 合金化对D88-Ti5Si3的结构稳定性和力学性质的影响. 结合态密度、差分电荷密度图和Mulliken 布居等电子结构分析, 揭示了Al 原子的添加量对D88-Ti5Si3的韧/脆性变化的影响机制. 研究表明, D88-Ti5Si3晶体中强的Ti6g―Si6g方向共价键是导致其室温脆性的主要原因. 当1 个和2 个Al 原子占据D88-Ti5Si3晶体中Si6g位置时, 形成了键强较弱的Al6g―Si6g键、Ti6g―Al6g键和Ti4d―Al6g键, 同时降低了D88-Ti5Si3中Ti6g―Si6g键的强度和数量, 从而提高了D88-Ti5Si3的韧性. 当D88-Ti5Si3晶体中Si6g位置被3个Al 原子所占时, Al6g―Si6g键消失, 而Ti6g―Si6g键的强度增加, 导致Ti5(Si1-xAlx)3的脆性增加.

关键词: 第一性原理, 钛硅化合物, 化学键, 韧/脆性, 电子结构

Abstract:

The influence of the substitution of Al for Si on the structural stability and mechanical properties of D88-Ti5Si3 was determined using first-principles pseudopotential plane-wave methods based on density functional theory. Several parameters including formation enthalpies ((ΔHf), cohesive energies (ΔEcoh), bulk modulus (B), shear modulus (G),Poisson's ratio (ν), Cauchy's pressure (C12-C66,C13-C44), metallicity (fm), and Peierls stress (τP-N) were calculated. To develop a better understanding of the effects of substitutional Al alloying on the toughness/brittleness of D88-Ti5Si3 from an electronic structure point of view the density of states, charge density differences and Mulliken population were determined. The results show that the intrinsic brittleness of D88-Ti5Si3 comes from strong covalent bonding between Ti6g and Si6g.When one or two Ti atoms occupy Si sites in the D88- Ti5Si3 crystal the intensity of covalent bonding between Ti6g and Si6g is reduced and the metallicity increases. This is accompanied by the presence of low intensity Al6g―Si6g, Ti6g―Al6g, and Ti4d―Al6g bonds. However, when three Ti atoms occupy Si sites in the D88-Ti5Si3 crystal the Al6g―Si6g bonds disappear and the intensity of covalent bonding between Ti6g and Si6g increases leading to an increase in brittleness.

Key words: First-principles, Titanium-silicon compound, Chemical bond, Ductile/brittle behavior, Electronic structure