Frist Principles Study Of Optical Properties Of Zn₁₂O₁₂ Cluster-assembled Porous Materials

Cluster-assembled materials with special structures and properties broaden us horizon.It’s development, has very important significance for the manufacturing of nano materials with tunable properties.In this paper, the electronic structures and optical properties as well as doping modification of four Zn12O12 cluster-assembled porous materials (FAU-ZnO、LTA-ZnO、R-ZnO、SOD-ZnO) have been studied in detail by first-principles calculations(GGA+U).Calculated results show that the band gap of zinc oxide with wurtzite phase (WZ-ZnO) is 3.41 eV,which is in agreed well with the experimental value of 3.44eV. The band gap of FAU-ZnO、LTA-ZnO、R-ZnO and SOD-ZnO is 3.84、4.06、3.55eV and 3.45eV,respectively, which are larger than that of WZ-ZnO. The band structures of four Zn12O12 cluster-assembled porous materials are similar with that of WZ-ZnO. The valence band is constitued mainly by 3d states of Zn and 2p states of O, and the conduction band mainly comes from 4s states of Zn and 2p states of O. In terms of optical properties, WZ-ZnO has the maximum absorption peak at 9eV. For SOD-ZnO phase and R-ZnO phase, the maximum absorption peak located at 13eV and 11eV, while the FAU-ZnO and LTA-ZnO phases have absorption peak at around 7eV. Compared to WZ-ZnO, SOD-ZnO phase and R-ZnO phase exist blue shift, While the FAU-ZnO and LTA-ZnO phases have red shifted absorption peak. As for the Cu doping, our results show that the band gap of WZ-ZnO, FAU-ZnO, LTA-ZnO, R-ZnO, and SOD-ZnO phases is reduced to 1.85,2.34,2.16,1.73eV and 1.67eV, respectively. As for the Co doping, it is found that the band gap of WZ-ZnO, R-ZnO and SOD-ZnO phases decreases to 1.76,1.78eV and 2.03eV, respectively. In optical properties, ZnO doped by Cu or Co results in absorption edge red shift phenomenon. Two kinds of elements improve ZnO phase in response to visible light with different degree. In addition, the change mechanism of the optical properties is analyzed. The results of our calculations for semiconductor cluster assembled materials provide an important guide for experimental study of such materials...