钛氢体系中氢和缺陷相互作用机制多尺度模拟研究

Titanium is one important kind of raw materials for devices used as hydrogen (including deurerium and tritium) storage applications due to its excellent hydrogen absoption/desorption capability and kinetics. The validity, reliability, and lifetime of these devices are tightly correlated with the H(D,T) interaction with the metal matrix during device maintainence and employment. So it would be an important project to study the envolvement of hydrogen in titanium solid solutions systems, and especially the interaction between hydrogen and defects in titanium. We will apply density functional theory (DFT) and density functional tight-binding (DFTB) method, to theoretically study the static and dynamical properties of the Ti-H(D,T) systems with defects, aimed at exploring and understanding the effects of hydrogen to structural, mechanical, and thermal, electrical conduction properties of these systems. The main contents include: 1) To verify and improve the DFTB parameters based on DFT calculations on several typical structure of titanium metal and hydrogen solid solutions; 2) To study the interactions betwen hydrogen and defects (e.g. dislocations) in titanium materials with considering some external conditions, e.g. temprature, strain, etc; 3) To study the effects of enviroments to the mechanism of local Ti-H structure evolement in hydrogen absortion process, and further the related mechanical and conductive properties. Based on our study, we are trying to build relations between micro structures and macro performaces of these systems with a relative large model, to clarify the micro mechanisms of the performace envolvement of these systems, and to supply some understanding and guidance to experimental and engingeering applications.

钛由于其优良的吸放氢性能，常用作储氢（氘，氚）的设备器件。器件的有效性、可靠性、寿命等，与存放及使用过程中氢（氘、氚）和金属相互作用的物理化学行为密切相关，因此理解氢在钛金属中的运动和演化，特别是氢与缺陷的相互作用是一个重要的研究课题。本项目将采用密度泛函理论和密度泛函紧束缚近似相结合的方法，理论研究钛氢体系中氢和缺陷的动态演化，探讨氢对材料结构以及力学、热学电学传导等性能的影响。主要研究内容包括：1）针对不同结构的钛金属，氢在其中的固溶体等，验证改进密度泛函紧束缚参数；2）利用得到的参数，研究在温度、应变等适当外部条件下，氢与材料中位错等缺陷的相互作用；3）以及这些作用对钛氢体系局域结构的影响及相应材料性能变化。通过本项目的研究，力争建立较大尺度模型的钛氢微观结构和性能的关系，并阐明此类体系性能演化的微观机制，并为相关的实验和工程应用提供一定的理解和指导。

本项目按研究计划开展理论研究和方法发展工作，并基本完成预期目标。主要研究要点集中在：氢与钛中孪晶界等缺陷的相互作用的结构及其对材料性能的影响，氢钛相互作用密度泛函紧束缚参数优化，不同氢化物和类似材料相稳定性的自由能研究。主要研究成果包括：（1）发展密度泛函紧束缚参数拟合工具jctc-fit，应用到不同比例钛氢化物，并扩展到锆；（2）认识不同浓度氢与孪晶界（11-21）的相互作用，从而对体系力学性质带来不同影响；（3）研究电子和振动的温度依赖对钛氢化物相稳定性的贡献，实现可包括非谐贡献的含温声子谱工具phonopy-tdep；（4）使用包括含温声子等方法研究了有类似相变的立方氮化钽的相稳定性。项目在执行期间，在J.Appl.Phys.，J.Phys.Chem.C，RSC Adv.等SCI期刊发表论文7篇。项目成员参加国内学术研讨会5人次。协助培养博士1名，硕士1名；在读硕士研究生1人。