Theoretical study of the molecular and electronic structures of neutral silver bromide clusters (AgBr)(n), n=1-9

The structures and UV absorption spectra of (AgBr)(n) clusters (n = 1-9) ar e investigated in both the gas phase and in a dielectric medium. The struct ures of clusters were determined at the B3P86 level using a moderate size b asis set with full geometry optimization. For clusters with n = 1-6, extens ive searches of the potential energy surface yielded only one minimum, whil e larger clusters displayed two or more minima. Qualitative aspects of the major UV absorption band were also explored. Experimentally, as the cluster s grow from monomers to larger systems, this band initially shifts to the b lue and then to the red. Our computational results parallel the experimenta l trends and show that the maximum blue shift occurs at the trimer or the t etramer. The molecular origin of the blue/red shift associated with AgBr cl uster growth can be readily explained by examining the orbital interactions which dominate the process and by the structure characteristics of the clu sters. Detailed molecular orbital energy level correlation diagrams for the dimerization, trimerization, and tetramerization are also presented.