Groupe de Chimie Théorique et Réactivité, ECP, IPREM UMR 5254, Université de Pau et de Pays de l'Adour, Hélioparc Pau Pyrénées 2 avenue du Président Angot, 64053 PAU Cedex 09, France.
J Chem Phys. 2011 Jul 28;135(4):044511. doi: 10.1063/1.3615499.
A global theoretical study of the (hyper)polarizabilities of alkali doped Si(10) is presented and discussed. First, a detailed picture about the low lying isomers of Si(10)Li, Si(10)Na, Si(10)K, Si(10)Li(2), Si(10)Na(2), and Si(10)K(2) has been obtained in a global manner. Then, the microscopic first (hyper)polarizabilities of the most stable configurations have been determined by means of ab initio methods of high predictive capability such as those based on the Møller-Plesset perturbation and coupled cluster theory, paying extra attention to the (hyper)polarizabilities of the open shell mono-doped systems Si(10)Li, Si(10)Na, Si(10)K, and the influence of spin contamination. These results were used to assess the performance of methods of low computational cost based on density functional theory (DFT) in the reliable computation of these properties in order to proceed with an in-depth study of their evolution as a function of the alkali metal, the cluster composition, and the cluster structure. The most interesting outcomes of the performed (hyper)polarizability study indicate that while alkali doping leaves the per atom polarizability practically unaffected, influences dramatically the hyperpolarizabilities of Si(10). The lowest energy structures of the mono-doped clusters are characterized by significantly enhanced hyperpolarizabilities as compared to the analogue neutral or charged bare silicon clusters Si(10) and Si(11), while, certain patterns governed by the type and the number of the doping agents are followed. The observed hyperpolarizability increase is found to be in close connection with specific cluster to alkali metal charge transfer excited states and to the cluster structures. Moreover, an interesting correlation between the anisotropy of the electron density, and the hyperpolarizabilities of these systems has been observed. Finally, it is important to note that the presented method assessment points out that among the various DFT functionals used in this work, (B3LYP, B3PW91, BhandHLYP, PBE0, CAM-B3LYP, LC-BLYP, LC-BPW91) only B3PW91 and PBE0 out of the seven provided a consistent quantitative performance for both polarizabilities and hyperpolarizabilities with respect to the ab initio methods utilized here. On the other hand, the long range corrected functionals LC-(U)BLYP and LC-(U)BPW91 (μ = 0.47) failed to supply quantitatively accurate hyperpolarizability results in all the studied clusters while the CAM-(U)B3LYP functional performs satisfactory only in the case of the Na and K doped systems.
本文对碱掺杂硅（10）的（超）极化率进行了全面的理论研究。首先，以全局的方式获得了 Si（10）Li、Si（10）Na、Si（10）K、Si（10）Li（2）、Si（10）Na（2）和 Si（10）K（2）的低能异构体的详细图像。然后，通过基于高预测能力的从头算方法，如基于 Møller-Plesset 微扰和耦合簇理论的方法，确定了最稳定构型的微观第一（超）极化率，并特别关注了开壳单核掺杂体系 Si（10）Li、Si（10）Na、Si（10）K 的（超）极化率以及自旋污染的影响。这些结果用于评估基于密度泛函理论（DFT）的低计算成本方法在可靠计算这些性质方面的性能，以便深入研究它们作为碱金属、团簇组成和团簇结构的函数的演化。所进行的（超）极化率研究的最有趣结果表明，虽然碱掺杂几乎不影响原子极化率，但却显著影响硅（10）的超极化率。单核掺杂团簇的最低能量结构与类似的中性或带电的纯硅团簇 Si（10）和 Si（11）相比，具有显著增强的超极化率，而特定的模式则受掺杂剂的类型和数量的控制。观察到的超极化率增加与特定的团簇到碱金属电荷转移激发态和团簇结构密切相关。此外，还观察到这些体系的电子密度各向异性与超极化率之间的有趣相关性。最后，需要注意的是，所提出的方法评估指出，在所研究的工作中使用的各种 DFT 泛函中（B3LYP、B3PW91、BhandHLYP、PBE0、CAM-B3LYP、LC-BLYP、LC-BPW91），只有 B3PW91 和 PBE0 与这里使用的从头算方法相比，对极化率和超极化率具有一致的定量性能。另一方面，长程修正泛函 LC-（U）BLYP 和 LC-（U）BPW91（μ = 0.47）在所有研究的团簇中都未能提供定量准确的超极化率结果，而 CAM-（U）B3LYP 函数仅在 Na 和 K 掺杂体系中表现出令人满意的性能。
