Dynamics Calculations of Several Atmospheric Reactions on Global Potential Energy Surfaces Público

Abstract

The potential energy surface (PES) plays a crucial rule in the computational simulation of chemical reactions. Sometimes, owing to the complexity of systems, only stationary points (minima and transition states) are characterized to represent the PES to explore reactions using statistical tools. However, the comprehensive and detailed dynamic studies call for global, full dimensional PES with accuracy. Recent progress by Braams and Bomwan enable us to construct the global potential energy surface of polyatomic system up to 10 atoms. The PES is mainly weighted least-square fit with respect to tens of thousands of high level ab initio electronic calculation energies. A critical ingredient of the PES is that it is made explicitly invariant under all permutations of like nuclei, and this property is built into the polynomial basis used for the fitting. Therefore, PES construction will be made routinely and more effort
could be made on system itself.

In atmospheric chemistry, there are lots of fundamental chemical reactions with very important implication of many crucial processes like catalytic cycles to produce ozone. Based on the constructed PES with key feature of invariance under all permutations of like nuclei, we can perform very detailed dynamics studies of many such fundamental reactions, like C+C2H2, OH+NO2, HO2+NO, and photodissociation of CH2CHCH2, CH2CDCH2, to explore microscopic mechanisms. With the good agreement between calculation results and experimental data, and more importantly, with detailed theoretical exploration to explain experimental mysterious results like in photodissociation of CH2CHCH2 case, the quasi-classical dynamics based on accurate high-level global PES are shown to be a powerful tool to investigate fundamental atmospheric chemical reactions.

Table of Contents

Contents
List of Tables viii
List of Figures ix
1 Introduction 1
2 Classical Trajectory Simulation on Potential Energy Surface 3
2.1 Ab Initio Potential Energy Construction . . . . . . . . . . . . . . . . 3
2.1.1 Potential Energy Function Representation . . . . . . . . . . . 4
2.2 Classical Trajectory Method . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Initial Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.1 Microcanonical normal mode sampling . . . . . . . . . . . . . 8
2.3.2 Angular Momentum Setup . . . . . . . . . . . . . . . . . . . . 9
2.3.3 Rotational Sampling for symmetric top polyatomic reactant . 11
2.3.4 Relative Position and Energy in Bimolecular Reaction . . . . . 12
2.4 Cross-Section and Rate Constant Calculation . . . . . . . . . . . . . 14
2.5 Final Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.5.1 Relative Velocity and Translation Energy . . . . . . . . . . . . 16
2.5.2 Velocity Scattering Angle . . . . . . . . . . . . . . . . . . . . 17
2.5.3 Internal Energy . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.5.4 Rotational Energy and Vibrational Energy . . . . . . . . . . . 18

3 Dynamics Calculations of C + C2H2 Reaction 19
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2 Tirplet and Singlet C3H2 Potential Energy Surface . . . . . . . . . . . 22
3.3 Dynamics Caculation Results . . . . . . . . . . . . . . . . . . . . . . 23
3.4 Summay and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 30

4 Surface-Hopping Trajectory Calculations of the C(3P)+C2H2 31
4.1 Surface-Hopping Dynamics Approach . . . . . . . . . . . . . . . . . . 31
4.1.1 Minima on the seam of crossing . . . . . . . . . . . . . . . . . 31
4.1.2 Transition probability . . . . . . . . . . . . . . . . . . . . . . 32
4.1.3 Dynamics setup and Transition scheme . . . . . . . . . . . . . 34
4.1.4 Estimate of Transition Probability . . . . . . . . . . . . . . . 37
4.2 Surface-hopping Dynamics Results and Discussion . . . . . . . . . . . 39
4.3 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . 43

5 Dynamics Calculation of the OH+NO2 Association Reaction 44
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.2 Potential Energy Surface Construction . . . . . . . . . . . . . . . . . 48
5.2.1 Fitting details . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
5.2.2 Properties of the PES . . . . . . . . . . . . . . . . . . . . . . 52
5.3 Quasiclassical Trajectory Calculations . . . . . . . . . . . . . . . . . . 56
5.3.1 Details of the calculation . . . . . . . . . . . . . . . . . . . . . 56
5.3.2 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . 57
5.4 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . 67

6 Path Integral Monte Carlo Calculation of CH5+ and CD3H2+ 69
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.1.1 CH5+ and CD3H2+ . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.1.2 Path Integral Monte Carlo Method . . . . . . . . . . . . . . . 70
6.1.3 Path Integral Monte Carlo Algorithm . . . . . . . . . . . . . . 72
6.2 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.2.1 CH5+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.2.2 CD3H2+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
6.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

7 Dynamics Calculation of the HO2+NO Association Reaction 81
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
7.2 Update on the OH+NO2 PES . . . . . . . . . . . . . . . . . . . . . . 83
7.3 Results and Disscussion . . . . . . . . . . . . . . . . . . . . . . . . . 86
7.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

8 A New Potential Energy Surface for CH3HCO 93
8.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
8.2 Updates on the CH3HCO PES . . . . . . . . . . . . . . . . . . . . . . 94

9 Dynamics Study of Dissociation of Allyl Radicals 98
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
9.2 C3H5 Potential Energy Surface Construction . . . . . . . . . . . . . 102
9.3 Trajecotry Setup and Analysis Method . . . . . . . . . . . . . . . . . 109
9.4 Dissociation of Allyl (CH2CHCH2) . . . . . . . . . . . . . . . . . . . 110
9.4.1 Hydrogen Elimination Channel . . . . . . . . . . . . . . . . . 112
9.4.2 Methyl Elimination Channel . . . . . . . . . . . . . . . . . . . 114
9.5 Dissociation of 2-d1-allyl CH2CDCH2 . . . . . . . . . . . . . . . . . 118
9.5.1 H/D Elimination Channel . . . . . . . . . . . . . . . . . . . . 118
9.5.2 CH3 or CH2D Elimination Channel . . . . . . . . . . . . . . . 120

9.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Bibliography 129

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School	Laney Graduate School
Department	Chemistry
Degree	PhD
Submission	Dissertation
Language	English
Research Field	Chemistry, Physical
Palavra-chave	Chao Chen's PhD thesis Quasiclassical Trajectory Calculation Potential Energy Surface
Committee Chair / Thesis Advisor	Bowman, Joel M, Emory University
Committee Members	Heaven, Michael, Emory University Kindt, James, Emory University

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