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σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. (Brinck group)ORCID iD: 0000-0003-3832-2331
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.ORCID iD: 0000-0003-2673-075X
2017 (English)In: Crystals, ISSN 2073-4352, Vol. 7, 222Article in journal (Refereed) Published
Abstract [en]

Understanding the molecular interaction behavior of transition metal nanoclusters lies at the heart of their efficient use in, e.g., heterogeneous catalysis, medical therapy and solar energy harvesting. For this purpose, we have evaluated the applicability of the surface electrostatic potential [VS(r)] and the local surface electron attachment energy [ES(r)] properties for characterizing the local Lewis acidity of a series of low-energy TM13 transition metal nanoclusters (TM = Au, Cu, Ru, Rh, Pd, Ir, Pt, Co), including also Pt7Cu6. The clusters have been studied using hybrid Kohn–Sham density functional theory (DFT) calculations. The VS(r) and ES(r), evaluated at 0.001 a.u. isodensity contours, are used to analyze the interactions with H2O. We find that the maxima of VS(r), σ-holes, are either localized or diffuse. This is rationalized in terms of the nanocluster geometry and occupation of the clusters’s, p and d valence orbitals. Our findings motivate a new scheme for characterizing σ-holes as σs (diffuse), σp (localized) or σd (localized) depending on their electronic origin. The positions of the maxima in VS(r) (and minima in ES(r)) are found to coincide with O-down adsorption sites of H2O, whereas minima in VS(r) leads to H-down adsorption. Linear relationships between VS,max (and ES,min) and H2O interaction energies are further discussed.

Place, publisher, year, edition, pages
MDPI AG , 2017. Vol. 7, 222
National Category
Physical Chemistry Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-211787DOI: 10.3390/cryst7070222Scopus ID: 2-s2.0-85026291822OAI: oai:DiVA.org:kth-211787DiVA: diva2:1131182
Note

20170816

Available from: 2017-08-13 Created: 2017-08-13 Last updated: 2017-11-29Bibliographically approved
In thesis
1. Computational Studies of Chemical Interactions: Molecules, Surfaces and Copper Corrosion
Open this publication in new window or tab >>Computational Studies of Chemical Interactions: Molecules, Surfaces and Copper Corrosion
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The chemical bond – a corner stone in science and a prerequisite for life – is the focus of this thesis. Fundamental and applied aspects of chemical bonding are covered including the development of new computational methods for the characterization and rationalization of chemical interactions. The thesis also covers the study of corrosion of copper-based materials. The latter is motivated by the proposed use of copper as encapsulating material for spent nuclear fuel in Sweden.

In close collaboration with experimental groups, state-of-the-art computational methods were employed for the study of chemistry at the atomic scale. First, oxidation of nanoparticulate copper was examined in anoxic aqueous media in order to better understand the copper-water thermodynamics in relation to the corrosion of copper material under oxygen free conditions. With a similar ambition, the water-cuprite interface was investigated with regards to its chemical composition and reactivity. This was compared to the behavior of methanol and hydrogen sulfide at the cuprite surface.

An overall ambition during the development of computational methods for the analysis of chemical bonding was to bridge the gap between molecular and materials chemistry. Theory and results are thus presented and applied in both a molecular and a solid-state framework. A new property, the local electron attachment energy, for the characterization of a compound’s local electrophilicity was introduced. Together with the surface electrostatic potential, the new property predicts and rationalizes regioselectivity and trends of molecular reactions, and interactions on metal and oxide nanoparticles and extended surfaces.

Detailed atomistic understanding of chemical processes is a prerequisite for the efficient development of chemistry. We therefore envisage that the results of this thesis will find widespread use in areas such as heterogeneous catalysis, drug discovery, and nanotechnology.

Abstract [sv]

Den kemiska bindningen – en hörnsten inom naturvetenskapen och oumbärlig för allt liv – är det centrala temat i den här avhandlingen. Både grundläggande och tillämpade aspekter behandlas. Detta inkluderar utvecklingen av nya beräkningsmetoder för förståelse och karaktärisering av kemiska interaktioner. Dessutom behandlas korrosion av kopparbaserade material. Det sistnämnda är motiverat av förslaget att använda koppar som inkapslingsmaterial för hanteringen av kärnavfall i Sverige.

Kvantkemiska beräkningsmetoder enligt state-of-the-art har använts för att studera kemi på atomnivå, detta i nära sammabete med experimentella grupper. Initialt studerades oxidation av kopparnanopartiklar under syrgasfria och vattenrika förhållanden. Detta för att bättre kartlägga koppar-vattensystemets termodynamik. Av samma orsak detaljstuderades även gränsskiktet mellan vatten och kuprit med fokus på dess kemiska sammansättning och reaktivitet. Resultaten har jämförts med metanols och vätesulfids kemiska beteende på ytan av kuprit.

En övergripande målsättningen under arbetet med att utveckla nya beräkningsbaserade analysverktyg för kemiska bindningar har varit att överbrygga gapet mellan molekylär- och materialkemi. Därför presenteras teoretiska aspekter samt tillämpningar från både ett molekylärt samt ett fast-fas perspektiv. En ny deskriptor för karaktärisering av föreningars lokala elektrofilicitet har introducerats – den lokala elektronadditionsenergin. Tillsammans med den elektrostatiska potentialen uppvisar den nya deskriptorn förmåga att förutsäga samt förklara regioselektivitet och trender för molekylära reaktioner, och för interaktioner på metal- och oxidbaserade nanopartiklar och ytor.

En detaljerad förståelse av kemiska processer på atomnivå är en nödvändighet för ett effektivt utvecklande av kemivetenskapen. Vi förutspår därför att resultaten från den här avhandlingen kommer att få omfattande användning inom områden som heterogen katalys, läkemedelsdesign och nanoteknologi.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 143 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:35
Keyword
computational chemistry, density functional theory, chemical interactions, reactivity descriptors, copper corrosion, surface and materials science, nucleophilic substitution reactions, heterogeneous catalysis, transition metal oxides, nanotechnology, beräkningskemi, täthetsfunktionalteori, kemiska interaktioner, reaktivitetsdeskriptorer, kopparkorrosion, yt- och materialvetenskap, nukleofila substitutionsreaktioner, heterogen katalys, överångsmetalloxider, nanoteknologi
National Category
Chemical Sciences Materials Chemistry Organic Chemistry Physical Chemistry Theoretical Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-213028 (URN)978-91-7729-506-8 (ISBN)
Public defence
2017-09-29, F3 (rumsnr: 132), Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170829

Available from: 2017-08-29 Created: 2017-08-28 Last updated: 2017-08-29Bibliographically approved

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Publisher's full textScopushttp://www.mdpi.com/2073-4352/7/7/222/htm

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