间隙原子在核石墨中迁移与结合规律的模拟计算  

Simulation calculation of the migration and combination of interstitial atoms in nuclear graphite

作　　者：徐海婷 吴喜军[1] 刘卫[2] 谭捷 杨果[2] 邓柯 张铭军 钱楠[2] 彭志华[1] XU Haiting;WU Xijun;LIUWei;TAN Jie;YANG Guo;DENG Ke;ZHANG Mingjun;QIAN Nan;PENG Zhihua(School of Mathematics and Physics,University of South China,Hengyang 421001,China;Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201800,China)

机构地区：[1]南华大学数理学院,衡阳421001 [2]中国科学院上海应用物理研究所,上海201800

出　　处：《核技术》2021年第6期58-64,共7页Nuclear Techniques

基　　金：湖南省自然科学基金面上项目(No.2018JJ2321);湖南省教育厅优秀青年项目(No.18B263);中国科学院上海应用物理研究所育新计划项目(No.YX2019007)资助。

摘　　要：为明确核石墨中间隙原子的存在形态与演化规律,利用第一性原理模拟研究间隙原子间的相互作用及其迁移、结合行为。研究表明:同一石墨片层上的间隙原子间存在引力,间距大于0.5 nm时其相互作用能可忽略;间隙原子倾向于沿扶手椅形方向迁移、结合,两间隙原子结合后降低的结构能约为6.0 e V;在间隙原子迁移过程中,整个迁移、结合反应的能垒约为0.4 eV;石墨中间隙原子最稳定的团簇结构是链状结构,紧邻的螺旋间隙原子结构次之,当结合的间隙原子数目超过6以后,间隙原子的结构将以包含六元碳环的团簇与底面以AB堆垛的形态存在,这是新石墨片层生成的重要机制。[Background]The interstitial atoms in nuclear graphite of the reactor will lead to the change of the properties and structure of the nuclear graphite.However,the migration and configuration of interstitial atoms in nuclear graphite are not well understood.[Purpose]This study aims to clarify the migration and combination mechanism of interstitial atoms in nuclear graphite by First-principles calculation.[Method]In this research,the Vienna Ab-initio Simulation Package was used to calculate the properties of the system.First-principles calculation was used to study the interaction between interstitial atoms and the migration and combination behavior of interstitial atoms.The diffusion energy barrier was estimated by the climbing image nudge elastic band(CI-NEB)method.[Results]There is a gravitational force between the interstitial atoms on the same graphite sheet,but it can be negligible while the distance between two interstitial atoms is greater than 0.5 nm.The interstitial atoms tend to migrate and combine along the armchair direction.The combination of two interstitial atoms reduces the structural energy by about 6.0 eV.The energy barrier of the entire migration and combination is about 0.4 eV during the migration process.[Conclusion]The most stable cluster structure of interstitial atoms in graphite is the chain-like structure,and the secondary is the spiro structure of the closely adjacent interstitial atoms.When the number of interstitial atoms is more than 6,the structure of interstitial atoms exists as a cluster containing six-membered carbon rings and stacked with the bottom surface vertically into an AB configuration.If more interstitial atoms are combined,a new graphite sheet will eventually be formed.

关 键 词：核石墨 间隙原子 第一性原理 迁移与结合 

分 类 号：TL341[核科学技术—核技术及应用]