Masters Theses

Phalgun Lolur

Abstract

"This thesis is about the development of robust methods for construction of global potential energy surfaces to study the spectroscopy and dynamics of molecular systems. A potential energy surface represents the electronic energy of a molecule as a function of its geometry. This is central to how chemists view molecular systems in terms of motion across a rich energy landscape where barriers separate wells corresponding to different stable structures. The range of molecular distortions defines the potential energy surface. Computing the potential energy surface of a molecule has become a fundamental operation in modern theoretical chemistry studies. The Born-Oppenheimer approximation simplifies the Schrödinger equation (since the nuclei move slowly relative to the electrons), and enables computation of energies forming the surface. In order to develop a highly accurate surface, it is generally required to compute energies at many (typically thousands) molecular geometries. These data are then fit together using an interpolative scheme to form an analytic function. Due to interaction between states, in order to develop a surface for a particular state of interest, one often needs to include several states. In a multistate calculation, states are optimized for some choice of relative weights. It is necessary to dynamically adjust the weights, as the geometry is varied, in order to obtain a smooth and continuous surface (as using fixed weights can lead to disruptive discontinuities where states switch character). This project developed a weighting scheme based on an energy dependent functional designed to produce high accuracy and robust convergence for global surfaces. This method has been successfully demonstrated on ozone. The theoretical calculations are in good agreement with experiments, producing a significant improvement of the rate constant for the O + O₂ exchange reaction"--Abstract, page iii.

Advisor(s)

Forciniti, Daniel
Dawes, Richard

Committee Member(s)

Wang, Jee C.

Department(s)

Chemical and Biochemical Engineering

Degree Name

M.S. in Chemical Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2013

Pagination

vii, 58 pages

Note about bibliography

Includes bibliographical references (pages 49-51).

Rights

© 2013 Phalgun Lolur, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Potential energy surfaces -- Design and constructionPotential energy surfaces -- Mathematical modelsPotential energy surfaces -- Computer simulationPotential energy surfaces -- AnalysisOzone -- Mathematical modelsOzone -- Computer simulation

Thesis Number

T 10295

Electronic OCLC #

853507815

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