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Theoretical modeling of X-ray spectroscopy of liquids
KTH, School of Biotechnology (BIO).
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , viii, 47 p.
Keyword [en]
Theoretical chemistry
Keyword [sv]
Teoretisk kemi
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-187ISBN: 91-7178-021-1 (print)OAI: oai:DiVA.org:kth-187DiVA: diva2:7851
Public defence
2005-05-13, FA32, AlbaNova, 13:00
Opponent
Supervisors
Note
QC 20101101Available from: 2005-05-10 Created: 2005-05-10 Last updated: 2011-11-23Bibliographically approved
List of papers
1. Local structures of liquid water studied by x-ray emission spectroscopy
Open this publication in new window or tab >>Local structures of liquid water studied by x-ray emission spectroscopy
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2004 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 2Article in journal (Refereed) Published
Abstract [en]

The O Kalpha x-ray emission spectra of water clusters with different sizes and conformations embedded in a continuum medium are simulated. The calculations have successfully explained the experimental spectra of water in both gas and liquid phases. It is shown that the x-ray emission spectra are very sensitive to the local hydrogen bonding structures. Strong electron sharing between different water molecules is observed and its possible connection to the covalency of hydrogen bonding is discussed. The experimentally observed strong excitation energy dependence of the spectra has been interpreted in terms of the polarization and angular dependence for the gas phase, and in terms of variations of local hydrogen bonding structures for the liquid phase.

Keyword
hydrogen-bond, ice, h2o, dynamics, spectrum, energy, dimer
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-23171 (URN)10.1103/PhysRevB.69.024201 (DOI)000188947300033 ()2-s2.0-1442326242 (Scopus ID)
Note
QC 20100525 QC 20111031Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2011-10-31Bibliographically approved
2. Electronic structure of water clusters in tetrahedral, ring, and chain conformations.
Open this publication in new window or tab >>Electronic structure of water clusters in tetrahedral, ring, and chain conformations.
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(English)Manuscript (preprint) (Other academic)
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-25808 (URN)
Note
QC 20101101Available from: 2010-11-01 Created: 2010-11-01 Last updated: 2010-11-01Bibliographically approved
3. Conformations and core-excitation dynamics liquid water.
Open this publication in new window or tab >>Conformations and core-excitation dynamics liquid water.
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(English)Manuscript (preprint) (Other academic)
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-25809 (URN)
Note
QC 20101101Available from: 2010-11-01 Created: 2010-11-01 Last updated: 2010-11-01Bibliographically approved
4. Molecular structure of alcohol-water mixtures
Open this publication in new window or tab >>Molecular structure of alcohol-water mixtures
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2003 (English)In: Physical Review Letters, ISSN 0031-9007, Vol. 91, no 15Article in journal (Refereed) Published
Abstract [en]

We use x-ray emission spectroscopy to elucidate the molecular structure of liquid methanol, water, and methanol-water solutions. We find that molecules in the pure liquid methanol predominantly persist as hydrogen-bonded chains and rings with six and/or eight molecules of equal abundance. For water-methanol solutions we find evidence of incomplete mixing at the microscopic level. Our results provide a new explanation for a smaller entropy increase in the solution due to water molecules bridging methanol chains to form rings.

Keyword
liquid methanol, diffraction, simulation, clusters, neutron
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-22880 (URN)10.1103/PhysRevLett.91.157401 (DOI)000185862500043 ()
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2010-11-01Bibliographically approved
5. Chemical and electronic structures of liquid methanol from x-ray emission spectroscopy and density functional theory.
Open this publication in new window or tab >>Chemical and electronic structures of liquid methanol from x-ray emission spectroscopy and density functional theory.
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2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 71, no 10Article in journal (Refereed) Published
Abstract [en]

We have applied x-ray emission spectroscopy and density functional theory (DFT) to study the chemical and electronic structures of liquid methanol. The x-ray emission spectra at carbon and oxygen K edges of methanol in different hydrogen-bonded clusters are simulated. It is shown that hydrogen bonding strongly influences the spectral profile of O K emission, but not the C K emission. The methanol chain and ring conformations show a distinct difference in their electronic structures. The molecular orbitals of chains are strongly localized, whereas for the ring structures they show strong delocalization characteristics and behaviorlike covalent pi orbitals in a conjugated system. A comparison of experimental spectra and DFT calculations suggests that liquid methanol comprises combinations of rings and chains of methanol molecules linked with hydrogen bonds and is dominated by structures with the size of six and eight molecules.

Keyword
initio molecular-dynamics, neutron-diffraction, methyl-alcohol, microwave-spectrum, room-temperature, basis-sets, energy, approximation, simulation, surface
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-14650 (URN)10.1103/PhysRevB.71.104205 (DOI)000228065400028 ()2-s2.0-20344369545 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-11-01Bibliographically approved
6. Molecular dynamics simulations and X-ray emission studies of Mg2+ cation in liquid water.
Open this publication in new window or tab >>Molecular dynamics simulations and X-ray emission studies of Mg2+ cation in liquid water.
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(English)Manuscript (preprint) (Other academic)
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-25815 (URN)
Note
QC 20101101Available from: 2010-11-01 Created: 2010-11-01 Last updated: 2010-11-01Bibliographically approved
7. Characterization of aza-fullerene C58N2 isomers by X-ray spectroscopy
Open this publication in new window or tab >>Characterization of aza-fullerene C58N2 isomers by X-ray spectroscopy
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2003 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 371, no 02-jan, 98-104 p.Article in journal (Refereed) Published
Abstract [en]

X-ray photoelectron and near-edge X-ray absorption fine-structure spectra (NEXAFS) of four isomers of C58N2 are predicted by means of density-functional theory calculations. A strong isomer dependence for both types of spectra are found. The spectroscopic findings are discussed in conjunction with results from electronic and geometric structure optimizations.

Keyword
carbon onions, films, (c59n)(2), xps
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-22360 (URN)10.1016/s0009-2614(03)00176-3 (DOI)000181788000016 ()
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2010-11-01Bibliographically approved
8. Electronic structure of carbon nitride thin films studied by X-ray spectroscopy techniques
Open this publication in new window or tab >>Electronic structure of carbon nitride thin films studied by X-ray spectroscopy techniques
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2005 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 471, no 02-jan, 19-34 p.Article in journal (Refereed) Published
Abstract [en]

Magnetron-sputtered carbon nitride thin films with different structures and compositions were analyzed by X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), as well as X-ray emission spectroscopy (XES). In all techniques, the carbon spectra are broad and featureless with little variation depending on growth conditions. The nitrogen spectra, on the other hand, show more distinct features, providing a powerful tool for structural characterization. By comparing the experimental spectra with calculations on different model systems, we are able to identify three major bonding structures of the nitrogen-N1: nitrile (C equivalent to N) bonds; N2: Pyridine-like N, i.e., N bonded to two C atoms; and N3: graphite-like N, i.e., N bonded to three C atoms as if substituted in a graphitic network, however, possibly positioned in a pentagon and/or with sp(3) carbon neighbors. The presence of N2 and N3 are best detected by XPS, while N1 is better detected by NEXAFS. The calculated XES spectra also give good indications how valence band spectra should be interpreted. Films grown at the higher temperatures ( greater than or equal to 350 degreesC) show a pronounced angular dependence of the incoming photon beam in NEXATS measurements, which suggests a textured microstructure with standing graphitic basal planes, while amorphous films grown at low temperatures show isotropic properties.

Keyword
X-ray spectroscopy, carbon nitride, thin film, absorption fine-structure, near-edge, high-resolution, photoelectron-spectroscopy, hardening mechanisms, thermal-stability, bonding structure, binding-energies, cnx films, spectra
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-14430 (URN)10.1016/j.tsf.2004.03.027 (DOI)000225724500003 ()2-s2.0-10644238092 (Scopus ID)
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2013-02-25Bibliographically approved

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