We present revised measurements of the static electric dipole polarizabilities of K, Rb, and Cs based on atom interferometer experiments presented in [Phys. Rev. A 2015, 92, 052513] but now re-analyzed with new calibrations for the magnitude and geometry of the applied electric field gradient. The resulting polarizability values did not change, but the uncertainties were significantly reduced. Then, we interpret several measurements of alkali metal atomic polarizabilities in terms of atomic oscillator strengths f(ik), Einstein coefficients A(ik), state lifetimes tau(k), transition dipole matrix elements D-ik, line strengths S-ik, and van der Waals C-6 coefficients. Finally, we combine atom interferometer measurements of polarizabilities with independent measurements of lifetimes and C-6 values in order to quantify the residual contribution to polarizability due to all atomic transitions other than the principal ns-np(J) transitions for alkali metal atoms.

No description available.

Carbon nanotubes have unique electronic, optical, mechanical, and transport properties which make them an important element of nanoscience and nanotechnology. However, successful application and integration of carbon nanotubes into new nanodevices requires fundamental understanding of their property changes under the influence of many external factors. This dissertation presents qualitative and quantitative theoretical understanding of property changes, while carbon nanotubes are exposed to the deformations, defects, external electric fields, and adsorption. Adsorption mechanisms due to Van der Waals dispersion forces are analyzed first for the interactions of graphitic materials and biological molecules with carbon nanotubes. In particular, the calculations are performed for the carbon nanotubes and graphene nanoribbons, DNA bases, and their radicals on the surface of carbon nanotubes in terms of binding energies, structural changes, and electronic properties alterations. The results have shown the importance of many-body effects and discrete nature of system, which are commonly neglected in many calculations for Van der Waals forces in the nanotube interactions with other materials at nanoscale. Then, the effect of the simultaneous application of two external factors, such as radial deformation and different defects (a Stone Wales, nitrogen impurity, and mono-vacancy) on properties of carbon nanotubes is studied. The results reveal significant changes in mechanical, electrical, and magnetic characteristics of nanotubes. The complicated interplay between radial deformation and different kinds of defects leads to the appearance of magnetism in carbon nanotubes which does not exist in perfect ones. Moreover, the combined effect of radial deformation and external electric fields on their electronic properties is shown for the first time. As a result, metal-semiconductor or semiconductor-metal transitions occur and are strongly correlated with the strength and direction of external electric field and the degree of radial deformations.

This dissertation focused on the potential use of highly charged nanoparticles to stabilize dispersions of weakly charged microparticles. The experimental components of the project centered on a model colloidal system containing silica microparticles at the isoelectric point where the suspensions are unstable and prone to flocculation. The stability of the silica suspensions was studied in the presence of highly charged nanoparticles. Initial experiments used polystyrene latex with either sulfate or amidine surface groups. Effective zeta potentials were measured with nanoparticle concentrations ranging from 0.001% to 0.5% vol. Adsorption levels were determined through direct SEM imaging of the silica microparticles, showing that the nanoparticles directly adsorbed to the microparticles (amidine more than sulfate), producing relatively large effective zeta potentials. However, stability experiments showed that the latex nanoparticles did not stabilize the silica but merely provided a reduction in overall flocculation rate. It was concluded that the zeta potential was an insufficient predictor of stability as there was still sufficient patchiness on the surface to allow for the silica surfaces to aggregate. Experiments using zirconia and alumina nanoparticles did achieve effective stabilization; both types stabilized the silica suspensions for longer than the observation period of approximately 15 hours. Stability was observed at concentrations of 10^-4% to 1.0% (zirconia) and 10^-2% vol. (alumina). These particles adsorbed directly to the microparticles (confirmed via SEM) and produced increasing effective zeta potentials with increasing nanoparticle concentrations. The adsorption resulted in significant electrostatic repulsion that was determined to be effectively irreversible using colloidal probe AFM. The improved stabilizing ability was attributed to the increased van der Waals attraction between the oxide nanoparticles (compared to polystyrene). Finally, an unexpected result of the CP-AFM force measurements showed that the repulsive forces between a nanoparticle-coated particle and plate lacked the normal dependence on the radius of the probe as predicted by the Derjaguin approximation. The forces observed in nanoparticle suspensions were virtually identical for 5 µm and 30 µm probes. Based on calculations of the shear rate in the gap, it was theorized that this phenomenon may have resulted from the shearing of adsorbed particles from the surfaces, which leads to similar interaction geometries for the two probe sizes. / Ph. D.

Van der Waals-Wechselwirkungen (vdW) sind allgegenwärtig und spielen eine zentrale Rolle in einer großen Anzahl biologischer und moderner synthetischer Materialien. Die am weitesten verbreitete theoretische Methode zur Berechnung von Materialeigenschaften, die Dichtefunktionaltheorie (DFT) in semilokaler Näherung, vernachlässigt diese Wechselwirkungen jedoch größtenteils, was zur Entwicklung vieler verschiedener vdW-Modelle führte. Die hier vorgestellte Arbeit ebnet den Weg hin zu einem vereinheitlichten vdW-Modell welches die besten Elemente der unterschiedlichen Klassen von vdW-Modellen vereint. Zu diesem Zweck haben wir einen vereinheitlichten theoretischen Rahmen geschaffen, der auf dem Reichweite-separierten Adiabatischer-Zusammenhang-Fluktuations-Dissipations-Theorem aufbaut und die meisten existierenden vdW-Modelle umfasst. Wir analysieren die MBD-korrelierte Wellenfunktion am prototypischen Beispiel von π–π-Wechselwirkungen in supramolekularen Komplexen und stellen fest, dass diese Wechselwirkungen größtenteils durch delokalisierte kollektive Ladungsfluktuationen entstehen. Um zu dem langreichweitigen vdW-Modell ein ausgewogenes kurzreichweitiges Dichtefunktional zu identifizieren, präsentieren wir eine umfassende Untersuchung zum Zusammenspiel der kurz- und langreichweitigen Energiebeiträge in acht semilokalen Funktionalen und drei vdW-Modellen für eine große Spanne von Systemen. Die Bindungsenergieprofile vieler der DFT+vdW-Kombinationen unterscheiden sich sowohl quantitativ als auch qualitativ stark voneinander. Schließlich untersuchen wir die Performance des Vydrov–Van Voorhis-Polarisierbarkeitsfunktionals über das Periodensystem der Elemente hinweg und identifizieren eine systematische Unterschätzung der Polarisierbarkeiten und vdW-C₆-Koeffizienten für s- und d-Block-Elemente. Als Lösung entwickeln wir eine orbitalabhängige Verallgemeinerung des Funktionals. / The ubiquitous long-range van der Waals interactions play a central role in nearly all biological and modern synthetic materials. Yet the most widely used theoretical method for calculating material properties, the density functional theory (DFT) in semilocal approximation, largely neglects these interactions, which motivated the development of many different vdW models. The work in this thesis paves way towards a unified vdW model that combines best elements from the different classes of the vdW models. To this end, we developed a unified theoretical framework based on the range-separated adiabatic-connection fluctuation--dissipation theorem that encompasses most existing vdW models. We analyze the MBD correlated wave function on the prototypical case of π–π interactions in supramolecular complexes and find that these interactions are largely driven by delocalized collective charge fluctuations. To identify a balanced short-range density functional to accompany the long-range vdW model, we present a comprehensive study of the interplay between the short-range and long-range energy contributions in eight semilocal functionals and three vdW models on a wide range of systems. The binding-energy profiles of many of the DFT+vdW combinations differ both quantitatively and qualitatively, and some of the qualitative differences are independent of the choice of the vdW model. Finally, we investigate the performance of the Vydrov—Van Voorhis polarizability functional across the periodic table, identify systematic underestimation of the polarizabilities and vdW C₆ coefficients for s- and d-block elements, and develop an orbital-dependent generalization of this functional to resolve the issue.

This thesis reports the design, synthesis, optical resolution of polypyridyl metal complexes and their molecular recognition of DNA. These metal complexes have been synthesised to bind DNA intercalation in a sequence selective manner. Modifications have manipulated the intercalative segments to bind to DNA in a rigid fashion by appending chemical groups directly to the aromatic extensions of the fragment. Also the ancillary non-intercalative ligands comprised of either bidentates or tetradentates, have been specifically chosen to deliver appended groups along the DNA sugar phosphate backbone, for hydrogen bonding and van der Waals interactions. Classical and chromatographic separation methods were investigated to separate the optical isomers of these ruthenium (II) complexes. A liquid recycling chromatography system was most successfully employed. Stereoselective synthesis was also investigated. Ultimately, it has been shown that the systematic modification of simple metal complexes is a useful method in determining the interactions of simple metal for nucleic acids. / Doctor of Philosophy (PhD)

No description available.

Atoms construct the molecules and molecules construct the material substances (with the exceptions as well, e.g.., metals, where atoms directly construct the material substances). Intermolecular interactions play an important role in most of the branches of sciences, ranging from material sciences to biological sciences. Van der Waals interactions are weak intermolecular interactions while hydrogen bonding varies in strength from weak to strong (1 to 40 kcal/mol). The present work focuses on applying some theoretical methods (ab initio and Atoms in Molecules theory) on these interactions to differentiate them with physically meaningful parameters such as hydrogen bond radii and atoms in molecules theory parameters. 1)Defining and calculating H-bond radii have been done using atoms in molecules theory approach which can explain ruling out the presence or absence of an H-bond in an intermolecular interaction. 2) A blue-shift of 200 cm-1 for a weakly bound complex is unprecedented. Our studies on weakly bound complexes showed the blue-shift of 200 cm-1 for H3C•••CIF and shift has been found to be purely from the mixing of normal modes and not because of an interaction. 3)Methane, a symmetric top molecule can act both as H-bond acceptor and donor. The present work shows that methane is rather a better H-bond acceptor than a donor and all the calculated parameters are in favor of this description. 4) Microwave spectrometer is an ultimate tool (at least at present) for structural characterization of the weakly bound complexes accurately. The rotational spectrum of the weakly bound isotopomer weakly bound complexes accurately. The rotational spectrum of the weakly bound isotopomer 13CC5H6•••Ar, which is a symmetric top and gives only “B” rotational constant. Moreover, the A rotational constant of the complex is the same as the rotational constant for 13CC5H6, which has no dipole moment. C2H2 molecule is an astrophysically important molecule as it is present in asymptotic giant branch and T-type stars (Teff<3000K). Due to its various infrared active vibrational modes, C2H2 is one of the most important sources in cool stars. The production of C2H2 infrared spectroscopic data at high temperature is therefore essential to trace back physical characteristics of these objects and to model the radiative transfer in their envelope. The databases such as “HITRAN”, do not have enough data available for stimulating high temperature spectra. Keeping all these objectives in mind, high temperature emission spectrum of acetylene has been recorded around 3µm region of acetylene.

During the last decades the specific manipulation of matter on the (sub-) nanometer scale, also known as nanoscience, became possible by technologies such as the scanning tunneling microscope. Nanocatalysts, i.e. catalytic active structures of up to a few nanometers in size, belong to this rather new class of materials. Unlike ordinary ’macroscopic’ catalytic materials, the performance of nanocatalysts does not simply scale, for instance, with the surface to volume ratio of the active material. In this Thesis model nanocatalysts are investigated by means of ab-initio density functional theory calculations. In paper I, we explain the experimentally observed catalytic characteristics of small gold clusters, Au1-4, on a regular magnesium oxide terrace towards the oxidation of carbon monoxide by thoroughly studying the adsorption of CO and O2 on these clusters. In the subsequent paper II, we study the feasibility of a catalytic water-mediated CO oxidation reaction on Au1-4/MgO and find that this reaction mechanism is not assessable for Au2,4/MgO and unlikely for Au1,3/MgO. Papers III and IV concentrate on the reactivity of clusters in the gas phase. Particularly, we focus on the relative stability of Au13 isomers and its potential for O2 dissociation (paper III). We find the lowest energy isomers, which contain a triangular prism at their center surrounded by a ring of the remaining seven atoms, to be generally stable upon O2 adsorption. The dissociation of O2 at certain sites of Au13 is found to be exothermic. In paper IV we performed scans of the Born-Oppenheimer potential energy surfaces of neutral and charged Cu3, Ag3, and Au3 to explore the thermally excited vibrations of these trimers. While the Born-Oppenheimer surface of Cu3 exhibits one fairly deep energy minimum, it is comparatively flat with two shallow minima in the case of Ag3. Hence for Ag3 there exist many thermally accessible geometries in a wide range of angles and bond lengths. For Au3, two distinct energy minima appear, being well-separated by a barrier of 180 meV. Already at room temperature, we find bond lengths changes of up to 5% for the studied trimers. Choosing Au3 as a case study for the changed reactivity of thermally excited modes, we find CO to bind up to 150 meV stronger to the excited cluster. Gold deposited on graphene and graphite was observed to form larger aggregates. In paper V, we study the electronic structures, high mobility, and substrate-mediated clustering processes of Au1-4 on graphene. Already in the 1970s is was speculated that dispersion forces, i.e. van der Waals forces, significantly contribute to the adsorption energies of gold atoms on graphite. We accounted for van der Waals interactions in our density functional theory calculations (paper VI) and investigated the influence of these dispersion forces on the binding of copper, silver, and gold adatoms on graphene. While copper and gold show a mixed adsorption mechanism, i.e. chemical binding plus attraction due to the van der Waals forces, silver is purely physisorbed on graphene. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 719

The Electron Localization Function (ELF) measures electron localization within matter and provides insights into the nature of bonds in materials and molecules. This thesis examines the relationship between ELF and binding energy in bimolecular systems, focusing on van der Waals interactions—specifically Keesom forces, Debye forces, and London dispersion forces—which play significant roles in molecular and crystalline materials. This research addresses the challenge of accurately calculating binding energies in crystalline materials by exploring their correlation with ELF. Using Density Functional Theory (DFT) with two exchange-correlation functionals, rev-vdW-DF2 and PBE-D3(BJ), this study proposes a method for calculating binding energies in crystalline materials with promising accuracy. By analysing the ELF and its correlation with binding energies in 75 bimolecular systems, the research demonstrates a strong linear correlation, with a coefficient of determination (R2) reaching up to 0.956. The findings suggest that ELF can effectively differentiate between weak and strong van der Waals interactions, providing a reliable metric for evaluating interaction strengths. The results indicate that ELF is a valuable tool for understanding the strength of molecular interactions, with potential applications in materials science and electronic structure theory. The study highlights the importance of refining the accuracy of the ELF-based method and expanding its scope to include other types of non-covalent interactions, such as halogen bonds. The main contribution of this thesis is the exploration of methodologies for analysing and predicting molecular interaction strengths within crystalline materials, which may improve computational approaches in the field. Deriving binding energies within the unit cell directly from the ELF has the potential to simplify practical calculations.