ABSTRACT

Over the recent past, semiconductor clusters with dimensions in the nanometer scale have become an active eld of research [1-4]. These nanoparticles represent a class of materials that span the physical domain between the bulk materials and a molecule. The interest in semiconductor nanoparticles stems from the fact that new properties are acquired at this length scale and it is equally important that these properties change with the size as well as the shape of the nanoparticles [5,6]. These size-and/or shape-dependent properties of semiconductor nanoparticles, which arise from the quantum connement effect promise new inventions and new materials with new interesting properties. The past couple of decades have witnessed an exponential growth of activities in this eld driven both by excitement of understanding new science and by the potential hope for technological applications and economic impacts. The largest activity in this eld at this time has been in the synthesis of new nanoparticles of different size and new shapes. The small size and large diversity in shapes of nanostructures are particularly attractive for exploring many unique and novel

12.1 Introduction .................................................................................................. 227 12.2 Theoretical Method ...................................................................................... 229 12.3 Results and Discussion ................................................................................. 233

12.3.1 Structure and Energetics ................................................................... 233 12.3.2 Electronic Properties ........................................................................ 237 12.3.3 HOMO-LUMO Gap ......................................................................... 237 12.3.4 Optical Properties .............................................................................240