钨中惰性气体杂质对He团簇的捕获：第一性原理预测和实验验证
Trapping of He Clusters by Inert-Gas Impurities in Tungsten: First-Principles Predictions and Experimental Validation
摘要：
采用第一性原理密度泛函理论（DFT）计算方法，系统地研究了体心立方钨中惰性气体原子引入引起的点缺陷的性质。间隙氖、氩、氪和氙原子的最稳定构型是四面体位置，类似于早先在W中发现的氦。计算的单个惰性气体原子的形成能在间隙网站，以及在替代网站是大得多的Ne，Ar，Kr和H2O比He。虽然惰性气体缺陷插入间隙配置的能量的变化可以解释由其大的原子尺寸的强烈影响，其替代能量所表现出的趋势更可能与惰性气体杂质原子和钨原子之间的共价相互作用。惰性气体杂质与空位之间的相互作用能有显著的变化，从He到Ne、Ar、Kr、Ar，都有明显的尺寸效应。这种趋势的起源可以通过电子结构计算来解释，电子结构计算表明p轨道在空位与四种惰性气体元素中任何一种的原子之间形成化学键的过程中起着重要的作用，而氦在外层中只包含1 s2电子。计算了氦原子被五种不同的缺陷（He-v，Ne-v，Ar-v，Kr-v，Xe-v，其中v表示bcc-W中的空位）俘获时的结合能，结果与热脱附谱的实验数据吻合得很好.本文分析了氦原子团簇与钨中惰性气体杂质原子陷阱的结合随连续俘获氦原子数目的变化。由于惰性气体杂质的杨氏模量的变化进行了分析的基础上，来自DFT计算的数据。
英文摘要：
Properties of point defects resulting from the incorporation of inert-gas atoms in bcc tungsten are investigated systematically using first-principles density functional theory (DFT) calculations. The most stable configuration for the interstitial neon, argon, krypton and xenon atoms is the tetrahedral site, similarly to what was found earlier for helium in W. The calculated formation energies for single inert-gas atoms at interstitial sites as well as at substitutional sites are much larger for Ne, Ar, Kr and Xe than for He. While the variation of the energy of insertion of inert-gas defects into interstitial configurations can be explained by a strong effect of their large atomic size, the trend exhibited by their substitutional energies is more likely related to the covalent interaction between the noble gas impurity atoms and the tungsten atoms. There is a remarkable variation exhibited by the energy of interaction between inert-gas impurities and vacancies, where a pronounced size effect is observed when going from He to Ne, Ar, Kr, Xe. The origin of this trend is explained by electronic structure calculations showing that p-orbitals play an important part in the formation of chemical bonds between a vacancy and an atom of any of the four inert-gas elements in comparison with helium, where the latter contains only 1s2 electrons in the outer shell. The binding energies of a helium atom trapped by five different defects (He-v, Ne-v, Ar-v, Kr-v, Xe-v, where v denotes a vacancy in bcc-W) are all in excellent agreement with experimental data derived from thermal desorption spectroscopy. Attachment of He clusters to inert gas impurity atom traps in tungsten is analysed as a function of the number of successive trapping helium atoms. Variation of the Young modulus due to inert-gas impurities is analysed on the basis of data derived from DFT calculations.
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