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Title:TDDFT calculations for excitation spectra of solids and superstructures utilizing mGGA
Author(s):Ning, Zhenhua
Director of Research:Chang, Yia-Chung
Doctoral Committee Chair(s):Stack, John D.
Doctoral Committee Member(s):Schleife, Andre; Hubler, Alfred W.
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Time-dependent Density Functional Theory (TDDFT)
semiconductor alloys
optical spectrum
Linearized Augmented Slater-type Orbital (LASTO)
meta-generalized gradient approximation (mGGA)
Local Density Approximation (LDA)
cluster averaging method
exchange-correlation potential
transition matrix element
Abstract:The first principles study plays a very important role in developing new generation of materials, such as organic semiconductors and long polymer chains, as well as understanding of physical properties of nanoparticles , inorganic semiconductors and semiconductor alloys. In this work, we start from the Kohn-Sham one-particle equation Schr¨odinger equation and solve it by expanding its eigenfunctions in terms of the linear augmented-slater-type orbits(LASTO) under full potential with the exchange-correlation potential functional given by meta-generalized gradient approximation(mGGA). Our theoretical results were compared to WIEN2K’s, and good agreement was obtained. As the application, we apply TDDFT plus mGGA to calculate optical spectra for bulk solids. The result shows good agreement with experimental data. III-V ternary alloys AxB1−xC are promising materials for optoelectronic, high-speed electronic and microwave applications, such as infrared emitting diodes and detectors, high electron mobility transistors, heterojunction bipolar transistors, quantum-dot lasers, modulators and ultrafast switches. We adopted the TDDFT theory and the cluster averaging method to compute the spectra of III-V ternary alloys with arbitrary concentration x. We find great agreement between theoretical and experimental data. The success of this method is mainly because that we approximate the transition matrix elements by the LDA p-matrix elements via (mGGA) which contains the singularity of the type fXC,00(q) ∼ 1/q2 as q → 0. Thus, Our studies provide some insight into the theoretical calculation of optical spectra of semiconductor alloys.
Issue Date:2015-04-13
Rights Information:Copyright 2015 Zhenhua Ning
Date Available in IDEALS:2015-07-22
Date Deposited:May 2015

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