Theoretical study on the structures and optical absorption of Si172 nanoclusters

Abstract

The structures and optical properties of silicon nanoclusters (Si NCs) have attracted continuous interest in the last few decades. However, it is a great challenge to determine the structures of Si NCs for accurate property calculation due to the complication and competition of various structural motifs. In this work, a Si₁₇₂ NC with a size of about 1.8 nm was investigated using a genetic algorithm combined with tight-binding and DFT calculations. We found that a diamond crystalline core with 50 atoms (1.2 nm) was formed in the Si₁₇₂ NC. It can be expected that at a size of about 172 atoms, a diamond crystalline structure can nucleate from the center of the Si NCs. The optical properties of the pure and hydrogenated Si₁₇₂ NC structures also have been studied using the TDDFT method. Compared with the pure Si₁₇₂ NC, the absorption peaks of the hydrogenated Si₁₇₂ NC are obviously blue-shifted.