Real-Space Calculations of Dielectric Screening in Large Silicon Nanocrystals

The nature of dielectric screening in semiconductor nanocrystals (NCs) is a outstanding topic. We examine the screening of a point charge in hydrogen-terminated Si NCs. We consider NC’s containing up to 5,400 atoms using 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 a P nucleus while maintaining the electron number. We consider NCs of sufficient size to converge the dielectric properties to the bulk limit. We find the resulting screening functions are consistent 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.