氦对LaNi5晶体结构的影响及其扩散特性研究

从密度泛函理论为基础的第一性原理出发，运用全势能线性缀加平面波(FLAPW)方法，对氚衰变后氦在合金中的占位以及LaNi₅He晶体结构进行了理论计算，并系统给出了氦在间隙间的迁移曲线.结果表明，氦原子在十二面体(1b)格位最稳定，并且氦从6m格位向1b格位迁移不存在势垒，而从2d格位向1b格位迁移则需越过1.55eV高的势垒.另外，氦从12n格位穿过12o格位最后到达6m格位也无明显势垒存在，并且处于4h格位之间的氦原子可以自由迁移，而相应12n格位之间的直接迁移则需跨越13.6eV高的势垒.最后还计算给出了氚衰变后合金的态密度、电子密度以及势能分布图，并与相应的LaNi₅H结构作了详细比较. 关键词： 全势能线性缀加平面波(FLAPW) 5He')" href="#">LaNi₅He 态密度 扩散

Theoretical studies on the structure and He interstitial diffusion of LaNi5He compounds

Based on the generalized gradient approximation (GGA) of density function and the full-potential linearized augmented plane wave (FLAPW) method, the micro-arrangement of He atoms after tritium decay in LaNi₅He have been modeled for theoretical study. The energy curves between 1b-6m-2d, 4h-2d-4h, 6m-12o-12n and 12n-3f-12n interstitial sites for LaNi₅He are worked out theoretically. The results indicate that 1b site is most stable for He occupation in LaNi₅He among the seven nonequivalent interstices. The potential barrier doesn't exist when He atoms migrate from 6m site to 1b site, but there is a potential barrier of height 1.55eV between 2d site and 1b site. And He atoms which lie in the 12n sites can easily go throngh the 12o sites to get to the 6m sites finally. Helium atoms can freely migrate between the 4h sites. By getting through a 13.6eV potential barrier, He atoms are able to directly migrate between the 12n sites. Finally, the density of states (DOS), charge density (CD) and potential distribution for characteristic interstitial LaNi₅He and LaNi₅H are plotted and compared with each other in detail.