Potential energy surface and applications to carbon dioxide-water, carbon dioxide clathrate hydrate and hydrated HCl system Público

Abstract

 

The potential energy surface is important to describe the molec- ular dynamics and molecular vibrations. In the first part of this thesis, an ab initio, full-dimensional, potential energy surface for CO2−H2O two-body interaction is presented. A full potential energy surface of dimer can be obtained by adding potentials for non-interacting monomers. Diffusion Monte Carlo calculations of the dimer zero-point energy are performed. Vibrational self-consistent and virtual-state configuration interaction method are used to characterize the vibrational eigenstates and energies. These results are in good agreement with experimental results. In addition, the CO2−H2O two-body potential energy surface is combined with existing water potential to develop a potential for the CO2 clathrate hydrate. A computationally efficient local-monomer treatment for this clathrate hydrate is presented. In the second part of the thesis, the vibrational predissociation of HCl−(H2O)3 cluster is studied. Using an existing potential energy surface, quasi-classical trajectory calculations were performed. This unimolecular decomposition can undergo two different pathways that were all observed by a large number of trajectory simulations. Information such as speed distribution, rotational energy distribution and branching ratio have been be obtained by analyzing final condition of the trajectories. 

Table of Contents

 

1 Introduction................................ 1

1.1 Introduction ................................ 1

1.2 Construction of the potential energy surface . . . . . . . . . . . . . . 1

1.3 Application of the potential energy surface . . . . . . . . . . . . . . . 3

1.4 Overview of the thesis........................... 4

2 Construction and application of PES for CO2−H2O and extension to the hydrate clathrate............... 6

2.1  Introduction ................................ 6

2.2  Theory and Computational Details.................... 11

2.2.1  Ab initio electronic energies databases. . . . . . . . . . . . . . 12

2.2.2  PES2b fitting............................ 13

2.2.3  Dissociation energy and vibrational analysis of the CO2−H2O dimer................................ 15

2.2.4  CO2 hydrate clathrate....................... 17

2.3  Results and Discussion .......................... 19

 

2.3.1 PES2b fitting precision....................... 19

2.3.2 Properties of the CO2−H2O PES ................ 21

2.3.3 Application to CO2@(H2O)20................... 26

 

2.4  Summary and conclusions ........................ 30

2.5  CO2−H2O software package........................ 31

3 Vibrational predissociation of HCl−(H2O)3 . . . . . . . . 32

3.1  Introduction ................................ 32

3.2  Theoretical methods and energetics ................... 34

3.3  Results and discussion........................... 38

 

3.3.1 Fragment Speed Distributions................... 38

3.3.2 Fragment Rotational Energy Distributions . . . . . . . . . . . 40

3.3.3 Dissociative Trajectories and Lifetimes. . . . . . . . . . . . . . 41

 

3.4  Summary and conclusions......................... 45

4 Summary .................................. 46 

About this Master's Thesis

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School	Laney Graduate School
Department	Chemistry
Degree	M.S.
Submission	Master's Thesis
Language	English
Research Field	Chemistry, Physical
Palavra-chave	quasi-classical trajectory computational chemistry carbon dioxide - water dimer MULTIMODE predissociation molecular dynamics VCI/VSCF hydrated HCl Vibrational spectrum carbon dioxide hydrate clathrate potential energy surface
Committee Chair / Thesis Advisor	Bowman, Joel, Emory University
Committee Members	Weaver, Susanna L. Widicus, Emory University Evangelista, Francesco, Emory University

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