Application of Lanczos-based time-dependent density-functional theory approach to semiconductor nanoparticle quantum dots

We present a density-functional theory study of Si nanoparticle quantum dots, focusing on determination of their optical properties. To calculate the absorption spectra of our quantum dot models we use a recently-developed method based on the application of Lanczos algorithms to linear-response time-dependent density-functional theory (LR-TDDFT). Quantum dot models are obtained by cutting Si atoms from the bulk crystal lattice and adding appropriate H terminating atoms to the surface; these structures are relaxed using density-functional theory in the plane-wave pseudopotential supercell approach, and then absorption spectra are calculated. We verify that with increasing size of the nanoparticle, the optical gap/onset of absorption steadily moves to lower energies. The paper represents an important demonstration of this new methodology on a class of systems that are the focus of significant current research in nanoscience.