Karamanis Panaghiotis, Bégué Didier, Pouchan Claude
Institut Pluridisciplinaire en Recherche sur l'Environnement et les Matériaux, UMR 5254 CNRS, Equipe de Chimie Physique, Groupe de Chimie Théorique, IFR, Rue Jules Ferry, BP 27540, F-64075 PAU, Cedex, France.
J Chem Phys. 2007 Sep 7;127(9):094706. doi: 10.1063/1.2768365.
We report reliable ab initio finite field (hyper)polarizability values at Hartree-Fock and second order Moller-Plesset perturbation theory (MP2) levels of theory for different geometrical configurations of small gallium arsenide clusters Ga(n)As(n) with n=2-5. We relied on all-electron basis sets and pseudopotentials suitable for (hyper)polarizability calculations. In each case, we used structures that have been established in the literature after we optimized their geometries at B3LYP/cc-pVTZ-PP level of theory. Our results suggest that the first order hyperpolarizability (beta) is much more sensitive to the special geometric features than the second order hyperpolarizability (gamma). For the most stable configurations up to ten atoms the second order hyperpolarizability at MP2 level of theory varies between 15 x 10(4) and 32 x 10(4) e(4)a0 (4)Eh(-3). In addition, we examined the polarizability per atom evolution versus the cluster size for Ga(n)As(n) with n=2-9. Our work extends earlier theoretical studies which were limited to eight atoms and exposes that the polarizability/atom of the most stable stoichiometric configurations up to Ga(9)As(9) continues the monotonic downward trend with increasing size. Lastly, from the methodological point of view, our analysis shows that apart from polarizabilities, augmented pseudopotentials yield reliable first and second hyperpolarizability values as well.
我们报告了在Hartree-Fock和二阶Moller-Plesset微扰理论（MP2）水平下，针对小砷化镓团簇Ga(n)As(n)（n = 2 - 5）不同几何构型的可靠的从头算有限场（超）极化率值。我们依赖于适用于（超）极化率计算的全电子基组和赝势。在每种情况下，我们使用了在文献中已确立的结构，并在B3LYP/cc-pVTZ-PP理论水平上对其几何构型进行了优化。我们的结果表明，一阶超极化率（β）比二阶超极化率（γ）对特殊几何特征更为敏感。对于多达十个原子的最稳定构型，在MP2理论水平下二阶超极化率在15×10⁴至32×10⁴ e⁴a₀⁴Eh⁻³之间变化。此外，我们研究了n = 2 - 9的Ga(n)As(n)团簇中每个原子的极化率随团簇大小的演变。我们的工作扩展了早期仅限于八个原子的理论研究，并表明直至Ga(9)As(9)的最稳定化学计量构型的每个原子的极化率随着尺寸增加继续呈现单调下降趋势。最后，从方法学的角度来看，我们的分析表明，除了极化率之外，增强赝势也能产生可靠的一阶和二阶超极化率值。
