A computational study of anion photoelectron spectroscopy of zinc oxide nanoclusters

The density functional theory (DFT) based calculations were carried out to study anion photoelectron spectroscopy of ZnO clusters. Detailed calculations were performed to study the molecular orbital configurations, molecular charge distributions, Mullikan’s atomic charge distributions, isosurface plots, thermodynamic properties, vibrational spectra and Franck Condon spectra of geometrically optimized ground states of neutral and anion structures of ZnO and (ZnO)2 clusters. The results indicated that the symmetric structure of ZnO cluster shows only one IR active mode whereas non-polar structure of (ZnO)2 shows six modes of vibration including three IR active modes. The Franck–Condon spectrum of these structures revealed that an increase in number of atoms in cluster causes an increase in number of Franck–Condon factors with a smaller overlap integral and an increase in depth of the potential well. Zero to zero ground state vibronic transition was observed to be most probable among all vibronic transitions with a Franck–Condon factor of 0.987 for ZnO and 0.982 for (ZnO)2 clusters.