Abstract
Noble metal nanoclusters are widely used in chemistry, nanotechnology, and biomedicine.However, the utility of silver (Ag) or gold (Au) nanoclusters for these applications is limited by
the lack of understanding of their fundamental properties. Quantum mechanical modeling has
been proven effective as a complement to experiments to provide insights into the metal
nanoclusters on the atomic scale. Semiempirical quantum mechanical methods (SEQMs) are
widely used in computational chemistry due to their low computational cost. The parametrization
of semiempirical methods was necessary due to insufficient experimental reference data on Ag
and Au nanoclusters at the time of development. In this dissertation, I parametrized PM7 (a
neglect of diatomic differential overlap method) for Ag and Au, specifically on obtaining
parameters that recreate the ground-state potential energy surfaces (PESs) of bare Ag and Au
clusters as well as thiol-protected Ag (AgSH) clusters. The resulting new parameters show
significant improvement relative to the default PM7 parameters for the binding energies, energy
changes upon displacement, and relative energies of isomers of these clusters. I also employed
the existing INDO/S Ag parameters to study charge transfer plasmons in Ag nanocluster dimers.
I have successfully shown that INDO/S is capable of quantifying the charge transfer characters in
the Ag dimer systems, which was not attainable previously by Time-dependent density
functional theory (TDDFT).