钠团簇范德华系数的含时密度泛函理论计算
Time-dependent density functional theory calculation of van der Waals coefficient of sodium clusters
摘要：
本文采用基于全电子\textit{ab-initio}含时密度泛函理论的方法，计算了含2 ~ 20个偶数原子的钠原子团簇的长程偶极-偶极色散系数（van der Waals系数）$C_{6}$.色散系数通过Casimir-Polder关系得到。用两种不同的交换关联势进行计算：（i）轨道势的渐近正确统计平均（SAOP）和（ii）局域密度近似下交换关联势的Vosko-Wilk-Nusair表示。与其他理论结果进行了比较。我们还介绍了钠团簇的静态极化率的结果，并与其他理论和实验结果进行了比较。这些比较表明，C_{6}和静态极化率的SAOP结果是相当准确的，非常接近的实验结果。我们研究了集群的体积和范德华系数之间的关系，发现C_{6}的相关性非常高的规模平方的体积。我们还给出了团簇-Ar原子和团簇- N_{2}分子相互作用对应的范德华系数的结果。
英文摘要：
In this paper we employ all-electron \textit{ab-initio} time-dependent density functional theory based method to calculate the long range dipole-dipole dispersion coefficient (van der Waals coefficient) $C_{6}$ of sodium atom clusters containing even number of atoms ranging from 2 to 20 atoms. The dispersion coefficients are obtained via Casimir-Polder relation. The calculations are carried out with two different exchange-correlation potentials: (i) the asymptotically correct statistical average of orbital potential (SAOP) and (ii) Vosko-Wilk-Nusair representation of exchange-correlation potential within local density approximation. A comparison with the other theoretical results has been performed. We also present the results for the static polarizabilities of sodium clusters and also compare them with other theoretical and experimental results. These comparisons reveal that the SAOP results for C_{6} and static polarizability are quite accurate and very close to the experimental results. We examine the relationship between volume of the cluster and van der Waals coefficient and find that to a very high degree of correlation C_{6} scales as square of the volume. We also present the results for van der Waals coefficient corresponding to cluster-Ar atom and cluster-N_{2} molecule interactions.
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