This book is based on my PhD thesis where I explored the electronic structure calculation of semiconductor quantum dots.All the calculations are based on density functional theory based ab-initio method.The optical properties of Silicon cluster and Quantum Confinement Effect were studied.Also the adsorption of Silicon clusters on metallic (Au/Ag) and insulating(MgO)surface were investigated in order to understand the charge transfer process between adsorbates and surfaces.This can be leading towards catalytic behavior as well studying the gas phase clusters on different surfaces.Also by...