氧原子在α钛晶体中扩散的第一性原理研究

发布时间：2018-03-07 04:22

本文选题：第一性原理　切入点：钛　出处：《物理学报》2017年11期 　论文类型：期刊论文

【摘要】：在材料领域杂质原子的迁移是一个基础而永恒的主题.采用基于密度泛函理论的第一性原理方法,研究了氧原子在α钛(α-Ti)晶体中的间隙占位情况,并计算了氧原子稳定占位点间隙能、电子态密度、电荷差分密度及其邻近钛原子的位移情况.采用基于过渡态搜索理论的CI-NEB(climbing image nudged elastic band)方法预测了稳定态氧原子在α-Ti晶体中的扩散路径、扩散势垒及相应的跳转频率,并由此推算出氧原子在不同位点之间跳转的扩散系数.研究结果表明,间隙氧原子在六角密排钛晶体结构中共有七种占位,但仅存在三个可稳定占据的间隙位点:八面体中心位点、六面体中心位点及0.28 nm钛—钛键中心位点.各稳定间隙位点之间的扩散具有不对称性,因此可确定三种稳定间隙氧原子位点间存在七条独立扩散路径.获取计算不同路径扩散系数所需要的微观参数,包括扩散势垒、扩散长度、不同扩散路径上鞍点氧原子的跳转频率,最终预测了不同间隙位点之间氧原子的扩散系数值,其中八面体中心扩散到邻近键位的扩散系数与实验值相符合.通过对间隙氧原子扩散行为的深入了解,希望能对控制钛合金中氧的扩散、提高钛金属中氧的含量及相关研究提供基础理论支持.
[Abstract]:The migration of impurity atoms in the field of materials is a fundamental and eternal subject. The gap occupation of oxygen atoms in 伪 -Ti crystals is studied by using the first-principle method based on density functional theory. The gap energy and electron density of states of oxygen atom are calculated. The CI-NEB(climbing image nudged elastic band method based on transition state search theory is used to predict the diffusion path, diffusion barrier and corresponding jump frequency of stable oxygen atoms in 伪 -Ti crystal. The diffusion coefficient of oxygen atoms jumping between different sites has been calculated. The results show that there are seven kinds of sites occupied by interstitial oxygen atoms in hexagonal dense titanium crystal structure. However, there are only three stable gap sites: octahedron central site, hexahedron central site and 0.28 nm Ti-Ti bond central site. Therefore, the existence of seven independent diffusion paths between three stable gap oxygen atom sites can be determined. The microscopic parameters needed to calculate the diffusion coefficients of different paths, including diffusion barrier, diffusion length, are obtained. Finally, the diffusion coefficient of oxygen atoms between different gap sites is predicted by the jump frequency of oxygen atoms at saddle points on different diffusion paths. The diffusion coefficient of octahedron center diffusion to the adjacent bond is in agreement with the experimental value. Through the deep understanding of the diffusion behavior of interstitial oxygen atoms, it is hoped that the diffusion of oxygen in titanium alloy can be controlled. Improving the content of oxygen in titanium metal and related research provide basic theoretical support.
【作者单位】：南京理工大学化工学院;海南大学材料与化工学院;
【基金】：国家自然科学基金(批准号:51361009) 海南大学青年基金(批准号:qnjj1239) 海南省自然科学基金(批准号:20155216)资助的课题~~
【分类号】：O76;TG146.23

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