Establishing framework of quantum Monte Carlo calculation on II-V semiconductor

Yu, Jaehyung

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https://hdl.handle.net/2142/89076 Copy

Description

Title

Establishing framework of quantum Monte Carlo calculation on II-V semiconductor

Author(s)

Yu, Jaehyung

Issue Date

2015-12-11

Director of Research (if dissertation) or Advisor (if thesis)

Ertekin, Elif

Department of Study

Mechanical Science & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• First principles
• Density functional theory (DFT)
• Quantam Monte Carlo (QMC)
• Zinc Oxide (ZnO)
• Zinc Selenide (ZnSe)

Abstract

Analyzing electronic properties of semiconductors in high accuracy is necessary for optoelectronic device application. First principles calculations are the best solution for evaluating the electronic properties of material, due to accurate description of quantum mechanical behavior of electrons. However, many body interaction of electrons restrict the size of calculations to few number of elec- trons. Density functional theory (DFT) is one of the solution, which circumvents the many body interaction problem by approximating it to e↵ective interaction between electron and averaged electron clouds. While it reduces calculation cost radically, mean-field approximation of DFT can yield inaccurate description of electronic properties especially for complex, wide band gap materials. Therefore, we introduces quantum Monte Carlo (QMC) method, which is an exciting technique with benchmark quality results. Instead of the mean- field interaction, QMC use stochastic approaches to solve the real Schr ̈odinger equation, which includes the many body interaction of electrons inherently. While QMC was hindered to be used due to large computational cost, current petascale computing machine and improved numerical algorithms enhance to use QMC in material simulation field. In order to use QMC method to material simulation, it is necessary to es- tablish proper frameworks for not only calculating material properties, but also analyzing error sources from the calculations. Here, we carried out system- atic assessment of QMC method for describing electronic properties of II–VI semiconductor ZnO and ZnSe. We categorized controllable, and uncontrollable errors of QMC calculations, and method to mitigate controllable errors such as finite size e↵ects and time step errors. Based on the established framework, we expect to utilize QMC to further complicated problems such as defect properties of the semiconductor.

Graduation Semester

2015-12

Type of Resource

text

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http://hdl.handle.net/2142/89076

Copyright and License Information

2015 by Jaehyung Yu. All rights reserved.

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