钨空位捕获氢及其解离过程的分子动力学  

Molecular dynamics study of trapping and detrapping process of hydrogen in tungsten vacancy

作　　者：付宝勤 侯氢[1] 汪俊[1] 丘明杰 崔节超 Fu Bao-Qin;Hou Qing;Wang Jun;Qiu Ming-Jie;Cui Jie-Chao(Key Laboratory for Radiation Physics and Technology,Ministry of Education,Institute of Nuclear Science and Technology,Sichuan University,Chengdu 610064,China)

机构地区：[1]四川大学原子核科学技术研究所辐射物理及技术教育部重点实验室

出　　处：《物理学报》2019年第24期38-45,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51501119)资助的课题~~

摘　　要：氢(H)同位素滞留问题是聚变堆第一壁材料设计的关键,而深入理解H在缺陷(如空位)处的非均匀形核长大过程有助于揭示H起泡及滞留的机制.针对第一壁材料钨(W)中空位捕获H及其解离的动力学过程开展研究,通过耦合捕获和解离两过程,构建新物理模型,避免了原单一过程的物理模型需准确记录相应事件首次发生时间的不足,另外新模型可同时提取解离系数和有效捕获半径等动力学参数.通过分子动力学模拟发现新模型能较好地描述W中空位-H复合体对H捕获和解离的动力学过程,根据空位-H复合体随时间的演化曲线,提取了有效捕获半径和解离系数等动力学参数.一方面能为动力学蒙特卡罗和速率理论等长时空尺度方法提供输入参数,另一方面促进了分子动力学的发展,进而实现了以较低计算资源获得更可靠的计算结果.Tungsten(W)alloys and W-based alloys are the primary candidate materials for plasma-facing components in future fusion reactors(e.g.ITER and CFETR).One of the critical issues still to be clarified in the design of the fusion reactor materials is the retention of hydrogen(H)isotopes in W,when the plasma-facing materials are supposed to sustain high-flux plasma and high-energy neutron.The dynamical behaviours of H in W with radiation defects(e.g.vacancy)are of serious concerns for understanding the mechanism of H capture,retention and permeation in W.In this work,a new model to extract the effective capture radius(ECR)and dissociation coefficient simultaneously is presented through coupling the trapping process and detrapping process of H in W vacancy.In the new model,the quantity ratio of vacancy to H atom in vacancy-H complex(VHx+1)in the molecular dynamics(MD)simulations is described as a function of time,while the exact occurrence time of corresponding event is not required.This new model,combined with extensive MD calculations,enables the simultaneous determining of the ECR and dissociation coefficient of H in W vacancy.It is found that the parameters are dependent not only on the event type but also on temperature.The dissociation energy of H from vacancy-H complex decreases gradually with the increase of the trapped number of H atoms in the vacancy-H complex.It is also found that the common assumption(i.e.the ECR is equal to one lattice constant and the pre-exponential factor is equal to 1013 s 1)in the long-term simulation methods(e.g.kinetic Monte Carlo and rate theory)is not always valid,since these calculated dynamical parameters are dispersive.The new model to obtain more reliable results with lower cost of computing resources can be easily extended into the other similar kinetic processes(e.g.H/He trapping and detrapping processes in other materials systems).These calculated dynamical parameters should be potentially helpful in supplying the initial input parameters for the long-term simulation methods

关 键 词：捕获半径 解离系数 分子动力学 空位 

分 类 号：G63[文化科学—教育学]