The structures of nanometer-sized silver clusters and their photographic properties

The electronic structures and geometries of nanometer-sized silver clusters Ag-n (n = 2-6) have been examined in the framework of self-consistent-field local density functional theory SCC-DV-X-alpha. The results show that there is a quantum size effect in silver clusters Ag-n. The binding energies per atom, E-b, for Ag-n increase monotonically with cluster size. There are transitions from a one-dimensional linear structure to a two-dimensional planar structure and then to a three-dimensional stereo structure from smaller silver clusters to larger ones. Both the binding energy differences, Delta E-b, between the neighbouring silver clusters and the highest occupied molecular orbital (HOMO) energies show these alternate features. The results indicate that the geometry factor takes an important role in the growth of nanometer-sized silver clusters. The steps from the one-dimensional linear structure (Ag-2) to the two-dimensional planar structure (Ag-3) and from the two-dimensional planar structure (Ag-4) to the three-dimensional stereo structure (Ag-5) are the hardest steps for the growth of these nanometer-sized silver clusters. After Ag-5, it is easier to grow by one silver atom for nanometer-sized silver clusters. The transition between structures of differ ent dimensional numbers can be treated as a kind of phase change. The results show the smallest development centre (A8(5)(+)) of the photographic process is the three-dimensional stereo structure of minimum size.