Electronic Structure of Ligated CdSe Clusters: Dependence on DFT Methodology

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• 作者：Victor V. Albert ; Sergei A. Ivanov ; Sergei Tretiak ; Svetlana V. Kilina
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：August 18, 2011
• 年：2011
• 卷：115
• 期：32
• 页码：15793-15800
• 全文大小：926K
• 年卷期：v.115,no.32(August 18, 2011)
• ISSN：1932-7455

文摘

Simulations of ligated semiconductor quantum dots (QDs) and their physical properties, such as morphologies, QD鈥搇igand interactions, electronic structures, and optical transitions, are expected to be very sensitive to computational methodology. We utilize Density Functional Theory (DFT) and systematically study how the choice of density functional, atom-localized basis set, and a solvent affects the physical properties of the Cd₃₃Se₃₃ cluster ligated with a trimethylphosphine oxide ligand. We have found that qualitative performance of all exchange-correlation (XC) functionals is relatively similar in predicting strong QD鈥搇igand binding energy (1 eV). Additionally, all functionals predict shorter Cd鈥揝e bond lengths on the QD surface than in its core, revealing the nature and degree of QD surface reconstruction. For proper modeling of geometries and QD鈥搇igand interactions, however, augmentation of even a moderately sized basis set with polarization functions (e.g., LANL2DZ* and 6-31G*) is very important. A polar solvent has very significant implications for the ligand binding energy, decreasing it to 0.2鈥?.5 eV. However, the solvent model has a minor effect on the optoelectronic properties, resulting in persistent blue shifts up to 0.3 eV of the low-energy optical transitions. For obtaining reasonable energy gaps and optical transition energies, hybrid XC functionals augmented by a long-range Hartree鈥揊ock orbital exchange have to be applied.