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

Qingfeng Wang (Spring 2018)

Permanent URL: https://etd.library.emory.edu/concern/etds/j6731380t?locale=zh
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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 CO2H2O 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 CO2H2O 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 CO2H2O 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 CO2H2O dimer................................ 15

2.2.4  COhydrate clathrate....................... 17

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

 

2.3.1 PES2b fitting precision....................... 19
2.3.2 Properties of the CO2H2O PES ................ 21
2.3.3 Application to CO2@(H2O)20................... 26

 

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

2.5  CO2H2O 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 

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