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Title: Modeling optical properties of silicon clusters by first principles: From a few atoms to large nanocrystals

Time dependent density functional tight binding (TDDFTB) method is implemented with sparse matrix techniques and improved parallelization algorithms. The method is employed to calculate the optical properties of various Si nanocrystals (NCs). The calculated light absorption spectra of small Si NCs from TDDFTB were found to be comparable with many body perturbation methods utilizing planewave basis sets. For large Si NCs (more than a thousand atoms) that are beyond the reach of conventional approaches, the TDDFTB method is able to produce reasonable results that are consistent with prior experiments. We also employed the method to study the effects of surface chemistry on the optical properties of large Si NCs. We learned that the optical properties of Si NCs can be manipulated with small molecule passivations such as methyl, hydroxyl, amino, and fluorine. In general, the shifts and profiles in the absorption spectra can be tuned with suitably chosen passivants.
Authors:
;  [1] ;  [1] ;  [2]
  1. Department of Physics and the Centre for Advanced 2D Materials, National University of Singapore, 2 Science Drive 3 (Singapore)
  2. (Singapore)
Publication Date:
OSTI Identifier:
22415687
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 15; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTRA; ALGORITHMS; ATOMS; CHEMISTRY; COMPARATIVE EVALUATIONS; DENSITY FUNCTIONAL METHOD; FLUORINE; HYDROXIDES; MANY-BODY PROBLEM; MOLECULES; NANOSTRUCTURES; OPTICAL PROPERTIES; PASSIVATION; PERTURBATION THEORY; SILICON; SURFACES; TIME DEPENDENCE; VISIBLE RADIATION