Theoretical Research On The Structures And Spectral Properties For Ti_n-mZr_mO_2n（n=2-7,0≤m≤n） Clusters

The ground-state geometrical structures, stability, electronic structures, infra-red (IR) and ultra-violet (UV) spectrum of the Tin-mZrmO2n (n=2-7,0≤m≤n) clusters have been investigated based on density functional theory in this paper.By using Gaussian09code, the geometrical structures of (TiO2)n (n=2-7) and Tin-mZrmO2n (n=2-7,0≤m≤n) clusters were optimized and the ground state geometries have been gotten. The calculated results show that the most stable structures for Tin-mZrmO2n clusters can be obtained in a way that Zr atoms substitute for Ti atoms connected to bridging oxygen atoms. The thermodynamic and kinetic stabilities of Tin-mZrmO2n clusters have been studied. For the same size Tin-mZrmO2n clusters, the binding energies increase approximately linearly with the increase of the number of Zr atoms, which means that the Tin-mZrmO2n cluster with more Zr atoms is relatively more stable. The HOMO-LUMO gap of Tin.mZrmO2n cluster can be adjusted by changing the number of Zr atom. Natural bond orbital (NBO) theory analysis shows that the charge transfer occurs among Ti, Zr and O atoms, indicating the formation of Ti-O-Zr bond in the mixed Tin-mZrmO2n clusters. The Ti-O-Zr bond is useful for improving the catalytic properties of TiO2.According to the IR spectrum analyses of Tin-mZrmO2n clusters, the Zr-O and Ti-O stretching motions from tenninal oxygen atoms led to the appearance of bands at900～1000cm-1and1000～1100cm-1, respectively; the vibrations of Ti-O-Zr-O four-membered rings give rise to the bands at600～800cm-1; the bands at800～900cm-1result from the motions of Ti-O or Zr-O six-membered rings.The UV spectra of the Tin-mZrmO2n clusters with ground state geometries were calculated by using time-dependent density functional theory (TDDFT). The blue shifts were observed for the UV spectra of the Tin-mZrmO2n clusters compared with those of the TinO2n and ZrnO2n clusters in the same size, except the TiZrO4cluster.