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Date Permissions Signed
5-28-2021
Date of Award
Spring 2021
Document Type
Masters Thesis
Department or Program Affiliation
Chemistry
Degree Name
Master of Science (MS)
Department
Chemistry
First Advisor
Kowalczyk, Tim
Second Advisor
Berger, Robert F.
Third Advisor
Gilbertson, John D.
Abstract
This research aims to implement a charge constraint in conjunction with a small configuration interaction scheme into a density-functional tight-binding (DFTB) method within the DFTB+ quantum mechanical software package. This method aims to model the electron transfer rate of chemical systems by calculating the electronic couplings between two constrained states more efficiently. Electronic couplings are directly proportional to electron transfer, making them important parameters to efficiently compute the optimal minimum or maximum of an electron transfer rate, for example, when screening chemical systems based on their ability as a conductor. Other methods such as constrained density-functional theory followed by a small configuration interaction scheme (CDFT-CI) developed by Wu and Van Voorhis can calculate electronic couplings. Still, as the complexity of chemical systems increases, the computational cost of CDFT-CI becomes intractable. Using CDFT-CI as a starting point, we can develop a constrained density-functional tight-binding followed by a small configuration interaction scheme (CDFTB-CI) to lower computational costs compared to CDFT-CI. The strategies to implement a CDFTB-CI option into DFTB+ utilize built-in features of DFTB+ while being as non-intrusive as possible. This process introduces a constraint option in DFTB+ with the capabilities of calculating constrained energies of constrained states of simple molecules, such as a set of simple homogeneous and heterogeneous dimers. This set of simple molecules can be used as case studies with the implications of finding the best practices for CDFTB.
Type
Text
Publisher
Western Washington University
OCLC Number
1254027180
Subject – LCSH
Density functionals--Methods; Oxidation-reduction reaction--Research; Computational chemistry; Solar cells--Research
Format
application/pdf
Genre/Form
masters theses
Language
English
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Recommended Citation
Carlson, Gunnar J., "Implementation of a Constraint and Configuration Interaction Methodology Into Density Functional Tight Binding" (2021). WWU Graduate School Collection. 1029.
https://cedar.wwu.edu/wwuet/1029