Evaluation of heat capacity of CdSe quantum dots using DFT calculations

Quantum confinement is a phenomenon that occurs upon successful control of size reduction of a semiconducting material below its exciton Bohr radius, which evolved to become quantum confined structures (QCSs), which are molecular-like, showing discrete energy transitions. These structures have been...

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Main Author:	Amirul Edham, Roslee
Format:	Thesis
Language:	English
Published:	2017
Subjects:	HD28 Management Industrial Management
Online Access:	http://umpir.ump.edu.my/id/eprint/19683/19/Evaluation%20of%20heat%20capacity%20of%20CdSe%20quantum%20dots%20using%20DFT%20calculations.pdf
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spelling	my-ump-ir.196832022-01-06T00:00:19Z Evaluation of heat capacity of CdSe quantum dots using DFT calculations 2017-03 Amirul Edham, Roslee HD28 Management. Industrial Management Quantum confinement is a phenomenon that occurs upon successful control of size reduction of a semiconducting material below its exciton Bohr radius, which evolved to become quantum confined structures (QCSs), which are molecular-like, showing discrete energy transitions. These structures have been widely explored for many applications as their physical (i.e., optical and electronic) properties are deviated substantially from those of bulk materials. This study attempted to evaluate thermophysical properties of QCSs, which specified in two research objectives; (i) to calculate the heat capacity of cadmium selenide (CdSe) quantum dots (QDs) using density functional theory (DFT), and (ii) to correlate the effect of size reduction of CdSe QDs with heat capacity and Debye temperature. Structure optimisation of CdSe QD clusters were performed using DFT calculations at the Becke’s three parameters with Lee-Yang-Parr generalised-gradient approximation corrected correlation (B3LYP) hybrid functional, together with Los Alamos effective core potential plus double-ζ quality (LanL2DZ) basis sets by Gaussian 09W program package. The optimised CdSe QD clusters were analysed by thermochemical calculations of 32 different temperatures from 5 to 400 K to determine thermophysical properties of CdSe QD clusters as a function of temperature. The results of thermochemical calculations of the optimised CdSe QD clusters comprised of (i) total electronic energies, (ii) zero-point energies, (iii) molar entropies, (iv) molar thermal energies, (v) molar constant-volume heat capacities, (vi) thermal enthalpies, (vii) thermal Gibbs free energies, and (viii) numbers of vibrational mode. Evaluation of heat capacities of CdSe QD clusters showed that the QDs do not exactly follow the Debye T3 model of heat capacity. In this work, from the phonon density of states it was proven that the dispersion relation follows a square root variation for QDs, which otherwise was a constant (speed of sound) according to the Debye T3 model, and subsequently the heat capacity of the QDs were shown to follow T3/2. The thermochemically-calculated heat capacity fit very well (> 99 %) to the T3/2 model. 2017-03 Thesis http://umpir.ump.edu.my/id/eprint/19683/ http://umpir.ump.edu.my/id/eprint/19683/19/Evaluation%20of%20heat%20capacity%20of%20CdSe%20quantum%20dots%20using%20DFT%20calculations.pdf pdf en public masters Universiti Malaysia Pahang Faculty of Industrial Science and Technology
institution	Universiti Malaysia Pahang Al-Sultan Abdullah
collection	UMPSA Institutional Repository
language	English
topic	HD28 Management Industrial Management
spellingShingle	HD28 Management Industrial Management Amirul Edham, Roslee Evaluation of heat capacity of CdSe quantum dots using DFT calculations
description	Quantum confinement is a phenomenon that occurs upon successful control of size reduction of a semiconducting material below its exciton Bohr radius, which evolved to become quantum confined structures (QCSs), which are molecular-like, showing discrete energy transitions. These structures have been widely explored for many applications as their physical (i.e., optical and electronic) properties are deviated substantially from those of bulk materials. This study attempted to evaluate thermophysical properties of QCSs, which specified in two research objectives; (i) to calculate the heat capacity of cadmium selenide (CdSe) quantum dots (QDs) using density functional theory (DFT), and (ii) to correlate the effect of size reduction of CdSe QDs with heat capacity and Debye temperature. Structure optimisation of CdSe QD clusters were performed using DFT calculations at the Becke’s three parameters with Lee-Yang-Parr generalised-gradient approximation corrected correlation (B3LYP) hybrid functional, together with Los Alamos effective core potential plus double-ζ quality (LanL2DZ) basis sets by Gaussian 09W program package. The optimised CdSe QD clusters were analysed by thermochemical calculations of 32 different temperatures from 5 to 400 K to determine thermophysical properties of CdSe QD clusters as a function of temperature. The results of thermochemical calculations of the optimised CdSe QD clusters comprised of (i) total electronic energies, (ii) zero-point energies, (iii) molar entropies, (iv) molar thermal energies, (v) molar constant-volume heat capacities, (vi) thermal enthalpies, (vii) thermal Gibbs free energies, and (viii) numbers of vibrational mode. Evaluation of heat capacities of CdSe QD clusters showed that the QDs do not exactly follow the Debye T3 model of heat capacity. In this work, from the phonon density of states it was proven that the dispersion relation follows a square root variation for QDs, which otherwise was a constant (speed of sound) according to the Debye T3 model, and subsequently the heat capacity of the QDs were shown to follow T3/2. The thermochemically-calculated heat capacity fit very well (> 99 %) to the T3/2 model.
format	Thesis
qualification_level	Master's degree
author	Amirul Edham, Roslee
author_facet	Amirul Edham, Roslee
author_sort	Amirul Edham, Roslee
title	Evaluation of heat capacity of CdSe quantum dots using DFT calculations
title_short	Evaluation of heat capacity of CdSe quantum dots using DFT calculations
title_full	Evaluation of heat capacity of CdSe quantum dots using DFT calculations
title_fullStr	Evaluation of heat capacity of CdSe quantum dots using DFT calculations
title_full_unstemmed	Evaluation of heat capacity of CdSe quantum dots using DFT calculations
title_sort	evaluation of heat capacity of cdse quantum dots using dft calculations
granting_institution	Universiti Malaysia Pahang
granting_department	Faculty of Industrial Science and Technology
publishDate	2017
url	http://umpir.ump.edu.my/id/eprint/19683/19/Evaluation%20of%20heat%20capacity%20of%20CdSe%20quantum%20dots%20using%20DFT%20calculations.pdf
_version_	1783732046149976064

Evaluation of heat capacity of CdSe quantum dots using DFT calculations

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