Change search
Link to record
Permanent link

Direct link
Hellström, Pär
Publications (5 of 5) Show all publications
Hellström, P., Larsson, A.-C., Fredriksson, A., Holmgren, A. & Öberg, S. (2008). Study of potassium O,O′-dibutyldithiophosphate combining DFT, 31P CP/MAS NMR and infrared spectroscopy (ed.). Journal of Physical Chemistry A, 112(46), 11777-11783
Open this publication in new window or tab >>Study of potassium O,O′-dibutyldithiophosphate combining DFT, 31P CP/MAS NMR and infrared spectroscopy
Show others...
2008 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 112, no 46, p. 11777-11783Article in journal (Refereed) Published
Abstract [en]

Dithiophosphates are used in many different industrial applications. To explain their functions and properties in these applications, a fundamental understanding on a molecular level is needed. Potassium O,O′-Dibutyldithiophosphate and its anion have been investigated by means of a combination of DFT and 31P CP/MAS NMR and infrared spectroscopy. Several low-energy conformations were studied by DFT. Three different conformations with significantly different torsion angles of the O-C bond relative to the O-P-O plane were selected for further studies of infrared frequencies and 31P NMR chemical-shift tensors. A good agreement between theoretical and experimental results was obtained, especially when the IR spectra or 31P chemical shift tensor parameters of all three conformations were added, indicating that, because of the low energy difference between the conformations, the molecules are rapidly fluctuating between them.

National Category
Physical Chemistry Computational Mathematics
Research subject
Chemistry of Interfaces; Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-9650 (URN)10.1021/jp805058a (DOI)000260926700031 ()18942802 (PubMedID)2-s2.0-57149144390 (Scopus ID)850ff0b0-b4a9-11dd-a6f7-000ea68e967b (Local ID)850ff0b0-b4a9-11dd-a6f7-000ea68e967b (Archive number)850ff0b0-b4a9-11dd-a6f7-000ea68e967b (OAI)
Note

Validerad; 2008; 20081117 (acla)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2023-10-14Bibliographically approved
Hellström, P., Holmgren, A. & Öberg, S. (2007). An ab initio study of ethyl xanthate adsorbed on Ge(111) surfaces (ed.). The Journal of Physical Chemistry C, 111(45), 16920-16926
Open this publication in new window or tab >>An ab initio study of ethyl xanthate adsorbed on Ge(111) surfaces
2007 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 45, p. 16920-16926Article in journal (Refereed) Published
Abstract [en]

The interaction between adsorbed ethyl xanthate on a clean Ge(111) surface and a hydroxylated surface was studied, using first-principle density functional theory. Geometrically optimized structures are presented and discussed. Results suggest a bidentate bridging conformation on a clean Ge(111) surface, whereas a monodentate bonding is preferred when the surface is saturated by hydrogen atoms. Then the interaction with a hydroxylated surface was considered. The lowest energy configuration was obtained when xanthate binds with one sulfur to the surface and with the other to an OH group adsorbed on the surface. A marker for this configuration was found in the vibrational spectra at 3200 cm-1. Vibrational frequencies down to 250 cm-1 were calculated and assigned to vibrational modes and presented together with the calculated infrared spectra. The tilt angle of the hydrocarbon chain was also investigated.

National Category
Computational Mathematics Physical Chemistry
Research subject
Scientific Computing; Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-10782 (URN)10.1021/jp074254j (DOI)000250836100032 ()2-s2.0-36749052363 (Scopus ID)9a4ae070-a992-11dc-9057-000ea68e967b (Local ID)9a4ae070-a992-11dc-9057-000ea68e967b (Archive number)9a4ae070-a992-11dc-9057-000ea68e967b (OAI)
Note

Validerad; 2007; 20071213 (alho)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2021-10-15Bibliographically approved
Fredriksson, A., Hellström, P., Öberg, S. & Holmgren, A. (2007). Comparison between in situ total internal reflection vibrational spectroscopy of an adsorbed collector and spectra calculated by ab initio density functional theory methods (ed.). The Journal of Physical Chemistry C, 111(26), 9299-9304
Open this publication in new window or tab >>Comparison between in situ total internal reflection vibrational spectroscopy of an adsorbed collector and spectra calculated by ab initio density functional theory methods
2007 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 26, p. 9299-9304Article in journal (Refereed) Published
Abstract [en]

In this investigation, adsorbed heptyl xanthate on a Ge(111) surface was studied, as well as the free heptyl xanthate molecule, by means of first-principle density functional theory calculations. The modeled results were compared with the in situ total internal reflection vibrational spectroscopy spectra of heptyl xanthate adsorbed on a germanium internal reflection element and the transmission infrared spectrum of a heptyl xanthate ion in aqueous solution. The assignments of the vibrational frequencies were done for the adsorbed xanthate. The region between 1150 and 1000 cm(-1) seems suitable for discussing differences between an adsorbed xanthate and its corresponding ion. The modeled spectra for both the adsorbed xanthate and the xanthate ion are in good agreement with the experimentally retrieved spectra. This investigation shows the strength of using DFT calculations in the interpretation of absorption bands from molecules adsorbed at surfaces in situ.

National Category
Physical Chemistry Computational Mathematics
Research subject
Chemistry of Interfaces; Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-6976 (URN)10.1021/jp071444l (DOI)000247599300045 ()2-s2.0-34547436294 (Scopus ID)54d99bc0-5ab5-11dc-8a1d-000ea68e967b (Local ID)54d99bc0-5ab5-11dc-8a1d-000ea68e967b (Archive number)54d99bc0-5ab5-11dc-8a1d-000ea68e967b (OAI)
Note

Validerad; 2007; 20070904 (pafi)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2021-10-15Bibliographically approved
Hellström, P., Öberg, S., Fredriksson, A. & Holmgren, A. (2006). A theoretical and experimental study of vibrational properties of alkyl xanthates (ed.). Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, 65(3-4), 887-895
Open this publication in new window or tab >>A theoretical and experimental study of vibrational properties of alkyl xanthates
2006 (English)In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 65, no 3-4, p. 887-895Article in journal (Refereed) Published
Abstract [en]

Geometrical structure and vibrational modes of potassium and sodium ethyl/heptyl xanthates were studied, using both theoretical and experimental methods. Both Hartree-Fock and density functional theory were used. The experimental method used was infrared absorption spectroscopy (FTIR). Our work showed that vibrational frequencies calculated with density functional theory, using the local density approximation, are in very good agreement with experiments. The results were not improved by using the more sophisticated and computationally demanding B3LYP functional.

National Category
Computational Mathematics Physical Chemistry
Research subject
Scientific Computing; Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-4794 (URN)10.1016/j.saa.2006.01.025 (DOI)000241785300060 ()16679053 (PubMedID)2-s2.0-33749338460 (Scopus ID)2c81d610-b06a-11db-840a-000ea68e967b (Local ID)2c81d610-b06a-11db-840a-000ea68e967b (Archive number)2c81d610-b06a-11db-840a-000ea68e967b (OAI)
Note

Validerad; 2006; 20070130 (ysko)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2021-12-13Bibliographically approved
Hellström, P. (2005). Ab initio modeling of xanthate adsorption on ZnS surfaces (ed.). (Licentiate dissertation). Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Ab initio modeling of xanthate adsorption on ZnS surfaces
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Modeling surface adsorption requires systems of hundreds of atoms. To model such systems at an ab initio level successfully, we need to avoid traditional quantum chemical methods. In the present work we have shown that density functional theory is a powerful modeling tool for large chemical systems especially in combinations with pseudopotentials This is validated by an initial study of ethyl and heptyl xanthates and their sodium/potassium salts. In this study, all electron calculations using both Hartree-Fock and density functional theory methods are compared with experimental infrared results. To do this the influence of basis sets and modeling approaches on the geometrical structure and the vibrational modes are examined. This includes comparing the pseudopotential and full electron potential approaches. Results obtained from pseudopotential methods are in close agreement with both all electron calculations as well as experimental results, here used to study adsorption of heptyl xanthate ZnS surfaces. Vibrational frequencies of the adsorbed species is presented, together with calculations of the tilt angles. The investigation of the tilt angles resulted in 20.3° 20.6° and 25.2° for the 100, 110 and 111 surfaces respectively. Heptyl xanthate forms a bridging confirmation on both the 110 and 111 surfaces and a bidentate confirmation on the 100 surface. Assignments of vibrational modes of ethyl/heptyl xanthate molecule and its corresponding potassium/sodium salts are also reported.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2005. p. 90
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757 ; 2005:37
National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-18069 (URN)6ad6c330-9ef4-11db-8975-000ea68e967b (Local ID)6ad6c330-9ef4-11db-8975-000ea68e967b (Archive number)6ad6c330-9ef4-11db-8975-000ea68e967b (OAI)
Note

Godkänd; 2005; 20070108 (haneit)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2024-03-28Bibliographically approved
Organisations

Search in DiVA

Show all publications