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Quantum and quantum-classical calculations of core-ionized molecules in varied environments
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. University of Oulu.ORCID iD: 0000-0003-1610-1431
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Computational quantum chemistry methods have been applied in two particular cases: to provide insight to photoionization induced fragmentation of HgBr2 and HgCl2 molecules, and to study core-electron binding energies and chemical shifts of molecules in liquid, surface adsorbed and polymeric environments in the framework of quantum mechanics/molecular mechanics (QM/MM). In the photodissociation studies the computational work is based on the relativistic Dirac equation as the systems present strong spin-orbit interaction affecting the fragmentation processes. In the QM/MM studies of ethanol-water mixtures and molecules physisorbed on silver surfaces the structures are provided by classical molecular dynamics simulations to analyze the distribution of the binding energies of core-orbitals and effects of their surroundings. In the case of polymethyl methacrylate polymer the impact of a QM-MM boundary and a polymeric environment are studied. The theoretical backgrounds of the computational methods applied and the obtained results are discussed.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2018. , p. 77
Series
TRITA-CBH-FOU ; 2018:20
Keywords [en]
Electron spectroscopy, UPS, XPS, photodissociation, binding energy, ionization potential, computational, electronic structure, self-consistent field, DFT, QM/MM, gas phase, liquid, solution, physisorption, metallic surface, polymer, charge transfer
National Category
Theoretical Chemistry
Research subject
Theoretical Chemistry and Biology
Identifiers
URN: urn:nbn:se:kth:diva-226919ISBN: 978-952-62-1882-3 (print)ISBN: 978-952-62-1883-0 (electronic)OAI: oai:DiVA.org:kth-226919DiVA, id: diva2:1202403
Public defence
2018-06-01, IT116, Univesity of Oulu, Pentti Kaiteran katu 1, 90014 Oulu, Finland, Oulu, 12:00 (English)
Opponent
Supervisors
Note

This thesis is for a double degree PhD done in KTH Royal institute of Technology and University of Oulu.

QC 20180502

Available from: 2018-05-02 Created: 2018-04-27 Last updated: 2018-05-08Bibliographically approved
List of papers
1. Spin-orbit interaction mediated molecular dissociation
Open this publication in new window or tab >>Spin-orbit interaction mediated molecular dissociation
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2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 18, p. 184304-Article in journal (Refereed) Published
Abstract [en]

The effect of the spin-orbit interaction to photofragmentation is investigated in the mercury(II) bromide (HgBr2) molecule. Changes in the fragmentation between the two spin-orbit components of Hg 5d photoionization, as well as within the molecular-field-splitted levels of these components are observed. Dissociation subsequent to photoionization is studied with synchrotron radiation and photoelectron-photoion coincidence spectroscopy. The experimental results are accompanied by relativistic ab initio analysis of the photoelectron spectrum.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-147743 (URN)10.1063/1.4873718 (DOI)000336782700068 ()2-s2.0-84904799578 (Scopus ID)
Note

QC 20140704

Available from: 2014-07-04 Created: 2014-07-03 Last updated: 2018-04-27Bibliographically approved
2. Fragmentation of mercury compounds under ultraviolet light irradiation
Open this publication in new window or tab >>Fragmentation of mercury compounds under ultraviolet light irradiation
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2015 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 143, no 7, article id 074307Article in journal (Refereed) Published
Abstract [en]

Ultraviolet light induced photofragmentation of mercury compounds is studied experimentally with electron energy resolved photoelectron-photoion coincidence techniques and theoretically with computational quantum chemical methods. A high resolution photoelectron spectrum using synchrotron radiation is presented. Fragmentation of the molecule is studied subsequent to ionization to the atomic-mercury-like d orbitals. State dependent fragmentation behaviour is presented and specific reactions for dissociation pathways are given. The fragmentation is found to differ distinctly in similar orbitals of different mercury compounds.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-173774 (URN)10.1063/1.4928651 (DOI)000360440400029 ()2-s2.0-84939857579 (Scopus ID)
Note

QC 20150921

Available from: 2015-09-21 Created: 2015-09-18 Last updated: 2018-04-27Bibliographically approved
3. Quantum Mechanics/Molecular Mechanics Modeling of Photoelectron Spectra: The Carbon 1s Core-Electron Binding Energies of Ethanol-Water Solutions
Open this publication in new window or tab >>Quantum Mechanics/Molecular Mechanics Modeling of Photoelectron Spectra: The Carbon 1s Core-Electron Binding Energies of Ethanol-Water Solutions
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2014 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 46, p. 13217-13225Article in journal (Refereed) Published
Abstract [en]

Using ethanolwater solutions as illustration, we demonstrate the capability of the hybrid quantum mechanics/molecular mechanics (QM/MM) paradigm to simulate core photoelectron spectroscopy: the binding energies and the chemical shifts. An integrated approach with QM/MM binding energy calculations coupled to preceding molecular dynamics sampling is adopted to generate binding energies averaged over the solutesolvent configurations available at a particular temperature and pressure and thus allowing for a statistical assessment with confidence levels for the final binding energies. The results are analyzed in terms of the contributions in the molecular mechanics modelelectrostatic, polarization, and van der Waalswith atom or bond granulation of the corresponding MM charge and polarizability force-fields. The role of extramolecular charge transfer screening of the core-hole and explicit hydrogen bonding is studied by extending the QM core to cover the first solvation shell. The results are compared to those obtained from pure electrostatic and polarizable continuum models. Particularly, the dependence of the carbon 1s binding energies with respect to the ethanol concentration is studied. Our results indicate that QM/MM can be used as an all-encompassing model to study photoelectron binding energies and chemical shifts in solvent environments.

National Category
Theoretical Chemistry Physical Sciences
Identifiers
urn:nbn:se:kth:diva-158401 (URN)10.1021/jp506410w (DOI)000345468600021 ()2-s2.0-84912530091 (Scopus ID)
Note

QC 20150109

Available from: 2015-01-09 Created: 2015-01-07 Last updated: 2018-04-27Bibliographically approved
4. Quantum mechanics capacitance molecular mechanics modeling of core-electron binding energies of methanol and methyl nitrite on Ag(111) surface
Open this publication in new window or tab >>Quantum mechanics capacitance molecular mechanics modeling of core-electron binding energies of methanol and methyl nitrite on Ag(111) surface
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2016 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 2, article id 024703Article in journal (Refereed) Published
Abstract [en]

We study a newly devised quantum mechanics capacitance molecular mechanics ( QMCMM) method for the calculation of core-electron binding energies in the case of molecules adsorbed on metal surfaces. This yet untested methodology is applied to systems with monolayer of methanol/methyl nitrite on an Ag(111) surface at 100 K temperature. It was found out that the studied C, N, and O 1s core-hole energies converge very slowly as a function of the radius of the metallic cluster, which was ascribed to build up of positive charge on the edge of the Ag slab. Further analysis revealed that an extrapolation process can be used to obtain binding energies that deviated less than 0.5 eV against experiments, except in the case of methanol O 1s where the difference was as large as 1.8 eV. Additional QM-cluster calculations suggest that the latter error can be connected to the lack of charge transfer over the QM-CMM boundary. Thus, the results indicate that the QMCMM and QM-cluster methods can complement each other in a holistic picture of molecule-adsorbate core-ionization studies, where all types of intermolecular interactions are considered.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-193238 (URN)10.1063/1.4956449 (DOI)000381153600036 ()27421423 (PubMedID)2-s2.0-84978481269 (Scopus ID)
Note

QC 20161010

Available from: 2016-10-10 Created: 2016-09-30 Last updated: 2018-04-27Bibliographically approved
5. Quantum-classical calculations of X-ray photoelectron spectra of polymers-Polymethyl methacrylate revisited
Open this publication in new window or tab >>Quantum-classical calculations of X-ray photoelectron spectra of polymers-Polymethyl methacrylate revisited
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2017 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 12, article id 124902Article in journal (Refereed) Published
Abstract [en]

In this work, we apply quantum mechanics/molecular mechanics (QM/MM) approach to predict core-electron binding energies and chemical shifts of polymers, obtainable via X-ray photoelectron spectroscopy (XPS), using polymethyl methacrylate as a demonstration example. The results indicate that standard parametrizations of the quantum part (basis sets, level of correlation) and the molecular mechanics parts (decomposed charges, polarizabilities, and capping technique) are sufficient for the QM/MM model to be predictive for XPS of polymers. It is found that the polymer environment produces contributions to the XPS binding energies that are close to monotonous with the number of monomer units, totally amounting to approximately an eV decrease in binding energies. In most of the cases, the order of the shifts is maintained, and even the relative size of the differential shifts is largely preserved. The coupling of the internal core-hole relaxation to the polymer environment is found to be weak in each case, amounting only to one or two tenths of an eV. The main polymeric effect is actually well estimated already at the frozen orbital level of theory, which in turn implies a substantial computational simplification. These conclusions are best represented by the cases where the ionized monomer and its immediate surrounding are treated quantum mechanically. If the QM region includes only a single monomer, a couple of anomalies are spotted, which are referred to the QM/MM interface itself and to the neglect of a possible charge transfer.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-205452 (URN)10.1063/1.4978941 (DOI)000397929300066 ()28388163 (PubMedID)2-s2.0-85016505625 (Scopus ID)
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2018-04-27Bibliographically approved

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