Dielectric Screening in Large Silicon Nanocrystals from Real-Space Pseudopotential Calculations

The nature of dielectric screening in semiconductor nanocrystals (NCs) is an continuing topic of interest. We examine the screening of a point charge in hydrogen-terminated Si NCs containing up to 5,400 atoms. Under the framework of pseudopotential-density-functional theory, we solve the Kohn-Sham equation in real-space using the PARSEC code. We compute the dielectric properties of a Si NC by replacing a Si nucleus at the center of the NC with an Al or P nucleus while maintaining the number of electrons. We consider NCs of sufficient size to converge the dielectric properties to the bulk limit. We contrast these results with previous studies on smaller NCs. The ability to calculate dielectric properties of a large confined system allows us to consider charged defects in bulk Si in a straight forward manner without invoking a compensating background.