From electronic structures to molecular-level cluster formation mechanisms in the atmosphere

Nanna Myllys

Tutkimustuotos: OpinnäyteVäitöskirjaArtikkelikokoelma

Kuvaus

Atmospheric aerosol particles affect the global climate and human health. A large fraction of atmospheric clusters is formed as a result of collisions and favourable interactions between molecules. However, the exact mechanisms and participating compounds are not fully resolved. The cluster formation mechanisms at the molecular-level are essential to understand what kind of effects aerosol particles have on climate change and health-related issues. Currently, aerosol particles provide the largest uncertainties in estimates of the future climate. In this thesis, potential cluster formation mechanisms between sulfuric acid and oxidized organic molecules with stabilizing compounds are studied using computational methods. Cluster stabilities must be determined accurately in order to provide trustworthy evaporation and formation rates in atmospheric conditions. This leads to the focus of this thesis: to evaluate the accuracy and applicability of different quantum chemical methods, and to find a robust methodology to study atmospheric cluster formation mechanisms and stabilities in the ambient air. Density functional theory is confirmed to be sufficient to optimize geometries and to calculate vibrational frequencies for molecular clusters. However, for binding energies high-level electronic structure calculations are necessary. The CCSD(T) method is known as the gold standard in quantum chemistry, but it is computationally too demanding for molecular clusters. Therefore, a domain-based local pair natural orbital (DLPNO) approximation is utilized. The DLPNO–CCSD(T) method allows highly accurate calculations for systems comprising more than hundred atoms. The formation energies can be calculated for atmospheric clusters containing up to ten molecules with an approach close to the CCSD(T) accuracy. Large clusters have previously been out of reach with highly accurate quantum chemical methods. The aim of the theoretical background in this thesis is to present an overview of quantum chemical methods. The introductory part of the thesis can be used as a handbook for problem solving related to molecular-level cluster formation mechanisms. The research presented here contributes significantly to the current knowledge of the participation of organic compounds in the first steps of aerosol particle formation. Additionally, this research suggests that some other mechanisms than clustering, or other chemical compounds are needed to bridge the gap between experimental and theoretical findings. Guidelines for future atmospheric cluster formation studies are given.
Alkuperäiskielienglanti
Myöntävä instituutio
  • Helsingin yliopisto
Valvoja/neuvonantaja
  • Vehkamäki, Hanna, Valvoja
  • Kurten, Theo, Valvoja
  • Elm, Jonas, Valvoja, Ulkoinen henkilö
Myöntöpäivämäärä1 joulukuuta 2017
JulkaisupaikkaHelsinki
Kustantaja
Painoksen ISBN978-952-7091-94-4
Sähköinen ISBN978-952-7091-95-1
TilaJulkaistu - 1 joulukuuta 2017
OKM-julkaisutyyppiG5 Tohtorinväitöskirja (artikkeli)

Tieteenalat

  • 116 Kemia

Lainaa tätä

Myllys, N. (2017). From electronic structures to molecular-level cluster formation mechanisms in the atmosphere. Helsinki: Finnish Association for Aerosol Research, FAAR.
Myllys, Nanna. / From electronic structures to molecular-level cluster formation mechanisms in the atmosphere. Helsinki : Finnish Association for Aerosol Research, FAAR, 2017. 175 Sivumäärä
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abstract = "Atmospheric aerosol particles affect the global climate and human health. A large fraction of atmospheric clusters is formed as a result of collisions and favourable interactions between molecules. However, the exact mechanisms and participating compounds are not fully resolved. The cluster formation mechanisms at the molecular-level are essential to understand what kind of effects aerosol particles have on climate change and health-related issues. Currently, aerosol particles provide the largest uncertainties in estimates of the future climate. In this thesis, potential cluster formation mechanisms between sulfuric acid and oxidized organic molecules with stabilizing compounds are studied using computational methods. Cluster stabilities must be determined accurately in order to provide trustworthy evaporation and formation rates in atmospheric conditions. This leads to the focus of this thesis: to evaluate the accuracy and applicability of different quantum chemical methods, and to find a robust methodology to study atmospheric cluster formation mechanisms and stabilities in the ambient air. Density functional theory is confirmed to be sufficient to optimize geometries and to calculate vibrational frequencies for molecular clusters. However, for binding energies high-level electronic structure calculations are necessary. The CCSD(T) method is known as the gold standard in quantum chemistry, but it is computationally too demanding for molecular clusters. Therefore, a domain-based local pair natural orbital (DLPNO) approximation is utilized. The DLPNO–CCSD(T) method allows highly accurate calculations for systems comprising more than hundred atoms. The formation energies can be calculated for atmospheric clusters containing up to ten molecules with an approach close to the CCSD(T) accuracy. Large clusters have previously been out of reach with highly accurate quantum chemical methods. The aim of the theoretical background in this thesis is to present an overview of quantum chemical methods. The introductory part of the thesis can be used as a handbook for problem solving related to molecular-level cluster formation mechanisms. The research presented here contributes significantly to the current knowledge of the participation of organic compounds in the first steps of aerosol particle formation. Additionally, this research suggests that some other mechanisms than clustering, or other chemical compounds are needed to bridge the gap between experimental and theoretical findings. Guidelines for future atmospheric cluster formation studies are given.",
keywords = "116 Chemical sciences",
author = "Nanna Myllys",
year = "2017",
month = "12",
day = "1",
language = "English",
isbn = "978-952-7091-94-4",
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From electronic structures to molecular-level cluster formation mechanisms in the atmosphere. / Myllys, Nanna.

Helsinki : Finnish Association for Aerosol Research, FAAR, 2017. 175 s.

Tutkimustuotos: OpinnäyteVäitöskirjaArtikkelikokoelma

TY - THES

T1 - From electronic structures to molecular-level cluster formation mechanisms in the atmosphere

AU - Myllys, Nanna

PY - 2017/12/1

Y1 - 2017/12/1

N2 - Atmospheric aerosol particles affect the global climate and human health. A large fraction of atmospheric clusters is formed as a result of collisions and favourable interactions between molecules. However, the exact mechanisms and participating compounds are not fully resolved. The cluster formation mechanisms at the molecular-level are essential to understand what kind of effects aerosol particles have on climate change and health-related issues. Currently, aerosol particles provide the largest uncertainties in estimates of the future climate. In this thesis, potential cluster formation mechanisms between sulfuric acid and oxidized organic molecules with stabilizing compounds are studied using computational methods. Cluster stabilities must be determined accurately in order to provide trustworthy evaporation and formation rates in atmospheric conditions. This leads to the focus of this thesis: to evaluate the accuracy and applicability of different quantum chemical methods, and to find a robust methodology to study atmospheric cluster formation mechanisms and stabilities in the ambient air. Density functional theory is confirmed to be sufficient to optimize geometries and to calculate vibrational frequencies for molecular clusters. However, for binding energies high-level electronic structure calculations are necessary. The CCSD(T) method is known as the gold standard in quantum chemistry, but it is computationally too demanding for molecular clusters. Therefore, a domain-based local pair natural orbital (DLPNO) approximation is utilized. The DLPNO–CCSD(T) method allows highly accurate calculations for systems comprising more than hundred atoms. The formation energies can be calculated for atmospheric clusters containing up to ten molecules with an approach close to the CCSD(T) accuracy. Large clusters have previously been out of reach with highly accurate quantum chemical methods. The aim of the theoretical background in this thesis is to present an overview of quantum chemical methods. The introductory part of the thesis can be used as a handbook for problem solving related to molecular-level cluster formation mechanisms. The research presented here contributes significantly to the current knowledge of the participation of organic compounds in the first steps of aerosol particle formation. Additionally, this research suggests that some other mechanisms than clustering, or other chemical compounds are needed to bridge the gap between experimental and theoretical findings. Guidelines for future atmospheric cluster formation studies are given.

AB - Atmospheric aerosol particles affect the global climate and human health. A large fraction of atmospheric clusters is formed as a result of collisions and favourable interactions between molecules. However, the exact mechanisms and participating compounds are not fully resolved. The cluster formation mechanisms at the molecular-level are essential to understand what kind of effects aerosol particles have on climate change and health-related issues. Currently, aerosol particles provide the largest uncertainties in estimates of the future climate. In this thesis, potential cluster formation mechanisms between sulfuric acid and oxidized organic molecules with stabilizing compounds are studied using computational methods. Cluster stabilities must be determined accurately in order to provide trustworthy evaporation and formation rates in atmospheric conditions. This leads to the focus of this thesis: to evaluate the accuracy and applicability of different quantum chemical methods, and to find a robust methodology to study atmospheric cluster formation mechanisms and stabilities in the ambient air. Density functional theory is confirmed to be sufficient to optimize geometries and to calculate vibrational frequencies for molecular clusters. However, for binding energies high-level electronic structure calculations are necessary. The CCSD(T) method is known as the gold standard in quantum chemistry, but it is computationally too demanding for molecular clusters. Therefore, a domain-based local pair natural orbital (DLPNO) approximation is utilized. The DLPNO–CCSD(T) method allows highly accurate calculations for systems comprising more than hundred atoms. The formation energies can be calculated for atmospheric clusters containing up to ten molecules with an approach close to the CCSD(T) accuracy. Large clusters have previously been out of reach with highly accurate quantum chemical methods. The aim of the theoretical background in this thesis is to present an overview of quantum chemical methods. The introductory part of the thesis can be used as a handbook for problem solving related to molecular-level cluster formation mechanisms. The research presented here contributes significantly to the current knowledge of the participation of organic compounds in the first steps of aerosol particle formation. Additionally, this research suggests that some other mechanisms than clustering, or other chemical compounds are needed to bridge the gap between experimental and theoretical findings. Guidelines for future atmospheric cluster formation studies are given.

KW - 116 Chemical sciences

M3 - Doctoral Thesis

SN - 978-952-7091-94-4

T3 - Report series in aerosol science

PB - Finnish Association for Aerosol Research, FAAR

CY - Helsinki

ER -

Myllys N. From electronic structures to molecular-level cluster formation mechanisms in the atmosphere. Helsinki: Finnish Association for Aerosol Research, FAAR, 2017. 175 s. (Report series in aerosol science; 206).