Theoretical Research On The Structures And Spectral Properties For Zinc,Cadmium And Mercury Dianion Clusers

The stability, aromaticity, electronic structure, infra-red and Raman vibration spectra of the Znn2-, Cdn2-and Hgn2"(n=3—8) clusters are studied by using density functional theory in this paper. The absorption spectra of the clusters are also calculated based on the time-dependent density functional theory. The results are as follows:1. With the increasing of the atomic number n, the stability of the Znn2-, Cdn2-and Hgn2-clusters decreases. Except for Zn62-, Cd62-and Hg72-clusters, the other Znn2", Cdn2-and Hgn2-clusters all show aromaticity, and for the same size clusters the aromaticity decreases in the order of Znn2, Cdn2-and Hgn2-. There is not direct relation between the stability and aromaticity for the Znn2-, Cdn2-and Hgn2-clusters.2. The electronic structure and bonding properties of the ground state Znn2-,Cdn2-and Hgn2-clusters have been studied by using NBO method. The atomic charges are in the range of-0.154e～-0.667e,-0.248e～0.667e and-0.247e～-0.667e for the Znn2-,Cdn2-and Hgn2-clusters, respectively. The hybrid orbits of s orbit with p orbit are formed and d orbits are not involved in bonding in all the clusters.3. The IR and Raman vibration spectra of the ground state Znn2-, Cdn2-and Hgn2-clusters have been investigated. The results show that if the vibration occurs in the fundamental frequency, the vibration intensity of this frequency will be the strongest among all the vibration frequencies. The IR and Raman vibration frequencies of the clusters are all in the far infrared region.4. The electronic absorption spectra of the Znn2-and Cdn2-clusters are calculated by using the time-dependent density functional theory. With the atomic number n increasing, the Znn2-clusters exhibit red shift UV-vis optical absorption spectra. The Cdn2-clusters show complex optical absorption properties. Compared with the Cd32" cluster, the optical absorption spectra of the Cdn2"(n=5—8) clusters all show red shift, while for the Cd42-cluster, blue shift occurs.