嵌入原子法计算金属钚中点缺陷的能量

Energy calculation of point defects in plutonium by embedded atom method

钚因放射性衰变而出现老化效应.钚中点缺陷的性质和行为是理解钚老化效应的一个基础和前提.运用分子动力学模拟技术,计算了金属钚中点缺陷和点缺陷团簇的形成能和结合能.其中钚-钚、钚-氦和氦-氦相互作用势分别采用嵌入原子多体势、Morse对势和Lennard-Jones对势.计算结果表明,单个自间隙原子易以〈100〉哑铃状形态存在;间隙氦原子在理想晶格的八面体间隙位置相对较为稳定;氦原子与空位的结合能较大,在钚的自辐照过程中两者易于结合并形成氦-空位团簇;氦-空位团簇的形成能随氦原子数的增加而增大,当氦与空位的数目相等时,组态较为稳定;晶界核心对氦原子和自间隙原子具有较强的俘获能力,对空位的俘获能力则相对要弱.

Plutonium is vulnerable to aging due to α radioactive decay.The properties and behaviors of point defects in plutonium are the basis for understanding plutonium aging.We have employed a molecular dynamics technique to calculate the formation energy and binding energy of point defects and small helium-vacancy clusters in plutonium,using embedded atom method,Morse pair potential and the Lennard-Jones pair potential for describing the interactions of Pu-Pu,Pu-He and He-He,respectively.A single self-interstitial atom＇s steady configuration is 〈100〉dumb-bell.An interstitial helium atom at octahedral site is more stable than that at tetrahedral site.As a result of high binding energy of an interstitial helium atom to a vacancy,helium atoms can combine with vacancies to form helium-vacancy cluster during the process of self-radiation.The formation energy of helium-vacancy cluster increases with the increasing number of helium atoms.When the number of helium atoms equals to the number of vacancy,the helium-vacancy cluster is rather stable.Both substitutional and interstitial helium atoms are trapped at the grain boundary（GB）.The binding energy of the self-interstitial atom at GB core is higher than that of helium atom and vacancy.