Lan You-Zhao, Feng Yun-Long
Zhejiang Key Laboratory for Reactive Chemistry on Solid Surfaces, Institute of Physical Chemistry, Zhejiang Normal University, Zhejiang, Jinhua 321004, China.
J Chem Phys. 2009 Aug 7;131(5):054509. doi: 10.1063/1.3195062.
We theoretically investigate the absorption spectra, dipole polarizabilities, and first-order hyperpolarizabilities of SiC(n) and Si(n)C (n=2-6) clusters using the density functional response approach. Similar to other semiconductor clusters such as Si and gallium arsenide (GaAs) clusters, the absorption spectra of the SiC(n) and Si(n)C clusters show long absorption tails in the low-transition-energy region and strong absorption peaks in the high-transition-energy region (>4.0 eV). For the same n, the absorption spectrum of the Si(n)C cluster is blueshifted with respect to that of the SiC(n) cluster, which may be related to the larger highest occupied molecular orbital-lowest unoccupied molecular orbital gap in the former. The isotropic (alpha) dipole polarizabilities of the SiC(n) and Si(n)C clusters are larger than the bulk polarizability of 3C-SiC and lie between the dipole polarizabilities of Si and C. The SiC(n) clusters have lower dipole polarizabilities and larger first-order hyperpolarizabilities than the Si(n)C clusters. The size dependence of the first-order hyperpolarizabilities of the SiC(n) clusters, which have approximate Si-terminated linear chain geometry, is similar to that observed in pi-conjugated organic molecules.
我们使用密度泛函响应方法从理论上研究了SiC(n)和Si(n)C（n = 2 - 6）团簇的吸收光谱、偶极极化率和一阶超极化率。与其他半导体团簇如Si和砷化镓（GaAs）团簇类似，SiC(n)和Si(n)C团簇的吸收光谱在低跃迁能区域呈现长吸收尾，在高跃迁能区域（>4.0 eV）呈现强吸收峰。对于相同的n，Si(n)C团簇的吸收光谱相对于SiC(n)团簇发生蓝移，这可能与前者较大的最高占据分子轨道 - 最低未占据分子轨道能隙有关。SiC(n)和Si(n)C团簇的各向同性（α）偶极极化率大于3C - SiC的体极化率，且介于Si和C的偶极极化率之间。SiC(n)团簇的偶极极化率低于Si(n)C团簇，但其一阶超极化率大于Si(n)C团簇。具有近似Si端接线性链几何结构的SiC(n)团簇的一阶超极化率的尺寸依赖性与在π共轭有机分子中观察到的类似。
