Investigation of Nano-particle Structures CdS using Density Functional Theory

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Mazloom Farsibaf, Hanieh | 2011

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 41669 (04)
University: Sharif University of Technology
Department: Physics
Advisor(s): Nafari, Naser; Rahimitabar, Mohammad Reza
Abstract:
In this project, we have studied the geometric and electronic structures of CdS nano-particles. The bulk CdS is known to be a semiconductor with the experimental energy gap of 2.42eV which is more than twice the theoretical resuls based on LDA or GGA energy functionals used in the density functional theory. However the calculations based on Kohn-Sham formalism used in DFT (KS-DFT) predicts the geometric structure of bulk semiconductors fairly well. Therefore, we have employed the KS-DFT formalism for our CdS nano-particles and have used the Gaussian as well as SIESTA computer codes to predict the geometric structures of these nano-semiconductor-particles. For calculating their electronic structures, in particular for calculating the HOMO-LUMO energy differences, we have studied the GW approximation. It is known that the GW approximation introduces corrections proportional to the renormalization factor, i.e., the discontinuity of electron-momentum distribution at the Fermi level. The agreement between the GWA results and experimens for bulk semiconductors are excellent. Hopefully, in our future work we will investigate the electronic structure of CdS nano-particles by way of GWA.
Keywords:
Density Functional Theory (DFT) ; Quantum Dot ; Cadmium Sulfide Nanoparticles ; Stable Structure

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