W_nNi_m(n+m=8)团簇的极性和光谱性质的理论研究

Theoretical study on polarities and spectrum properties of W_nNi_m(n+m=8) clusters

采用密度泛函理论(DFT)中的B3LYP方法,在LANL2DZ基组水平上对W_nNi_m(n+m=8)团簇的各种可能构型进行了几何参数全优化,得到了它们的基态构型;并对基态构型的偶极距、极化率、红外光谱和拉曼光谱性质进行了分析,结果表明:团簇W_nNi_m(n+m=8)都具有极性,富W团簇非线性光学效应强,容易被外加场极化;振动频率主要分布在0—350cm1范围内,团簇W_4Ni_4因其振动方式的特殊性,红外光谱和拉曼光谱在频率421.971cm^(-1)处,都有明显强峰;团簇W_5Ni_3因其结构的高对称性在振动光谱中出现多处共振现象.

The possible equilibrium geometries of WnNim （n＋m=8） clusters are optimized by using the density functional theory at the B3LYP/LANL2DZ level. For the ground state structures, the dipole moment, polarizability and vibrational spectrum are analyzed. The calculated results show that each of all the clusters of WnNim （n＋m=8） has a polarity, and W-rich clusters which have a strong nonlinear optical effect each and are easy to be polarized by external electromagnetic field, that vibrational frequencies are mainly distributed in a 0–350 cm-1 range, but the cluster of W4Ni4, due to the particularity of vibration mode, has a obviously strong peak on IR spectrum and also on Raman spectrum, each at a frequency of 421.971 cm-1, and that the W5Ni3 cluster, with high symmetry of C3v point group, presents a resonance phenomenon on IR spectrum.