摘要:
采用密度泛函理论中的广义梯度近似对Hg与小团簇Au^qn（n=1-6，q=0，＋1，-1）的相互作用进行了系统研究．结果表明，除Au5^＋,-团簇外，前线分子轨道理论可以成功预测大部分Au。Hg’复合物的最低能量结构．Aua团簇对Hg的吸附受团簇尺寸大小和团簇所携带电荷的影响较大．随着团簇尺寸的增加，中性Aua团簇对Hg的吸附能是先增加后减小；n=4时吸附能达到最大值（0．661eV）．阳离子团簇的吸附能随着团簇尺寸的增加逐渐减小；但在n=5处有一突起现象．阴离子Aua团簇中，除n=3外，其吸附能随团簇尺寸的增加亦是逐渐减小的．与中性和阴离子Aua团簇相比，阳离子团簇对Hg的吸附能力更强．对于最低能量结构的AunHg^q复合物，Hg的Mulliken电荷与吸附能的线性关系较明显．根据电荷转移的多少，可以较为准确地判断Aun^q团簇对Hg的吸附强弱．
关键词:
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密度泛函理论
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汞
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金团簇
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吸附能
Abstract:
Elemental mercury （Hg） adsorptions on small neutral, cationic and anionic gold clusters, Au^qn （n = 1-6, q = 0, ＋ 1, - 1 ）, are systematically investigated by using the density functional theory （DFT） in the generalized gradient approximation. The result shows that the frontier molecular orbital theory （FMOT） is useful for predicting the favorable binding configurations of Hg adsorbed on neutral and charged Aun clusters. Most of the lowest energy AunHg complexes can be successfully predicted. The size and the charge state of the clusters have strong influence on the adsorption of Hg on gold clusters. The adsorption energy on the neutral clusters reaches a local maximum at n = 4, which is about O. 661 eV. The adsorption energies for cationic clusters decrease with cluster size increasing, although there is a local peak at n = 5. Similarly, for anionic clusters, the adsorption energies decrease with cluster size, except for n = 3. The adsorption energies on the cationic clusters are generally stronger than those on the neutral and anionic clusters. For the lowest energy AuHg complexes, an approximate linear correlation between the adsorption energy and the Mulliken charge on adsorbed Hg is found. The more the charges transfer to the cluster, the higher the adsorption energy is.
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