Time-dependent molecular properties are important for the experimental characterization of molecular materials. We show how these properties can be calculated, for optical and x-ray frequencies, using novel quantum chemical methods. For xray absorption there are important relativistic effects appearing, due to the high velocity electrons near the atomic nuclei. These effects are treated rigorously within the four-component static exchange approximation. We also show how electron correlation can be taken into account in the calculation of x-ray absorption spectra, in time-dependent density functional theory based on the complex polarization propagator approach. The methods developed have been applied to systems of experimental interest|molecules in the gas phase and adsorbed on metal surfaces. The effects of molecular vibrations have been take into account both within and beyond the harmonic approximation.

This thesis deals with theoretical studies of the electronic structure of molecules used in the context of molecular electronics. Both studies with model Hamiltonians and first principle calculations have been performed. The materials studied include molecular crystals of pentacene and DNA, which are used as active material in field-effect transistors and as tentative molecular wires, respectively. The molecular magnet compound TCNE and surface modification by means of chemisorption of TDAE on gold are also studied. Molecular crystals of pentacene are reported to have the highest field-effect mobility values for organic thin film field-effect transistors. The conduction process in field-effect transistors applications occurs in a single layer of the molecular crystal. Hence, in studies of transport properties molecular crystals of pentacene can be considered as a two dimensional system. An open question of these system is if the charge transport is bandlike or if as a result of disorder is a hopping process. We address this question in two of the included papers, paper I and paper II. The conducting properties of DNA are of interest for a broad scientific community. Biologist for understanding of oxidatively damaged DNA and physicist and the electronics community for use as a molecular wire. Some reports on the subject classifies DNA as a conductor while other report insulating behavior. The outcome of the investigations are heavily dependent on the type of DNA being studied, clearly there is a big difference between the natural and more or less random sequence in, e.g., λ-DNA and the highly ordered syntethic poly(G)-poly(C) DNA. It has been suggested that long-range correlation would yield delocalized states, i.e., bandlike transport, in natural DNA, especially in the human chromosome 22. In paper III we show that this is not the case. In general our results show that DNA containing an approximately equal amount of the four basis is an insulator in a static picture. An emerging research field is spintronics. In spintronic devices the spin of the charge carrier is as important as the charge. One can envision a device where spin alone is the carrier of information. In realizing spintronic devices, materials that are both magnetic and semiconducting are needed. Systems that exhibit both these properties are organic-based magnets. In paper IV the electronic structure of the molecular magnet compound TCNE is studied, both experimentally and theoretically. The injection of carriers from metal contacts to organic semiconductors is central to the performance of organic based devices. The interface between the metal contact and the organic material has been pointed out to be one of the device parameters that most significantly influences the device performance. This relates to the process of injection of charge carriers in to the organic material. In some contact and organic material combinations the energy barrier for charge injection can be very high. The barrier can be reduced by modify the interface dipole, this is achieved by a monolayer of adsorbed molecules at the interface. The molecule TDAE chemisorbed on gold is studied in paper V.

Density functional theory has been used to investigate cathode materials for rechargeable batteries, carbon nanotube interactions with catalyst particles and transition metal catalyzed hydrogen release in magnesium hydride nanoclusters. An effort has been made to the understand structural and electrochemical properties of lithium iron silicate (Li2FeSiO4) and its manganese-doped analogue. Starting from the X-ray measurements, the crystal structure of Li2FeSiO4 was refined, and several metastable phases of partially delithiated Li2FeSiO4 were identified. There are signs that manganese doping leads to structural instability and that lithium extraction beyond 50% capacity only occurs at impractically high potentials in the new material. The chemical interaction energies of single-walled carbon nanotubes and nanoclusters were calculated. It is found that the interaction needs to be strong enough to compete with the energy gained by detaching the nanotubes and forming closed ends with carbon caps. This represents a new criterion for determining catalyst metal suitability. The stability of isolated carbon nanotube fragments were also studied, and it is argued that chirality selection during growth is best achieved by exploiting the much wider energy span of open-ended carbon nanotube fragments. Magnesium hydride nanoclusters were doped with transition metals Ti, V, Fe, and Ni. The resulting changes in hydrogen desorption energies from the surface were calculated, and the associated changes in the cluster structures reveal that the transition metals not only lower the desorption energy of hydrogen, but also seem to work as proposed in the gateway hypothesis of transition metal catalysis.

The absorption properties of the Pt1 chromophore at room temperature have been studied. Stretch, bend and torsion parameters for Pt(II), P, C (type 1, 2 and 4) and H have been parameterized for use in the MM3 force field. Parameters were fitted to energies computed at the B3LYP level of theory. The parameterized model was used to perform molecular dynamics simulations at room temperature. This was done for several environments and for time periods of up to 200 ps. Absorption properties were computed for snapshots from the dynamics, from which average absorption spectra were created. A conformational broadening of around 40 nm was found in the theoretical spectra, which is in good agreement with experiments. Due to a lack of solvent-solute interactions and the use of a less extensive basis set, a systematic blue shift of 40 nm is evident in the computed spectra.

The main purpose of this thesis is to implement the Gauss--Legendre quadrature for the dispersion coefficient. This has been done and can be now be made with different number of points. The calculations with this implementation has shown that the relativistic impact on helium, neon, argon and krypton is largest for krypton, that has the highest charge of its nucleus. It was also seen that the polarizability of neon as a function of the imaginary angular frequency decreases monotonically from a static value.

The goal of this thesis is to develop a constraint based viscoplastic fluid model suitable for time-efficient dynamics simulation in 3D of granular matter. The model should be applicable to both the static and dense flow regime and at large pressures. The thesis is performed for UMIT Research Lab at Umeå University. It is a part of the research at UMIT connected to LKAB and Volvo CE and its applications can be in simulating industrial processes or training simulators. My work is based on previous work done by Claude Lacoursière, Martin Servin and Kenneth Bodin. They have created a constraint fluid model based on {\sph} and Claude's PhD. thesis. This model is extended with additional constraints to handle shear forces, which is necessary to model granular material. Some test cases are specified and compared visually to each other and to the results of other work. The model seems to work visually but more analysis and larger systems are needed to be certain. The model should scale well and is well suited for parallellization.

<p>The X-ray absorption spectrum of silicon in of SiCl4 has been calculated for the LIII and LII edges. The resulting spectrum has been vibrationally resolved by considering the symmetric stretch vibrational mode and the results has been compared to experiment [4]. One peak from the experiment was found to be missing in the calculated vibrationally resolved spectrum. The other calculated peaks could be matched to the corresponding experimental peaks although significant basis set effects are present. An investigation of one peak beyond the Franck–Condon principle shows it to be a good approximation in the case of the studied system.</p>

In this thesis, we focus on theoretical study of adsorbates on metal and oxide surfaces that are important for surface chemistry and catalysis. Based on first principles calculations, the adsorption ofCO, NO, NO2, C4H6S2, C22H27SH and other molecules or radicals on nobel metal surfaces (gold and silver) are investigated. Also, NO oxidation on oxygen pre-covered Au(111)surface and CO oxidation on water-oxygen covered Au(111)surface aretheoretically studied. A new mechanism of water-enhanced COoxidation is proposed. As for oxide surfaces, we first investigatethe geometric, electronic and magnetic structures of FeO ultrathin film on Pt(111) surface. The experimentally observed scanning tunneling microscopy images are well reproduced for the first timewith our model. The adsorption and dissociation of water on rutileTiO2(110) surface are investigated by quantum molecular dynamics.By theoretical X-ray photoemission spectroscopy (XPS) calculations,the surface species are properly assigned. The same strategy has applied to the study of the phase transition of water covered reconstructed anatase TiO2(001) surface, from which two different phases are theoretically identified. The structure of graphene oxideis also studied by comparing experimental and theoretical XPS spectra. Based on the novel structures identified, a new cutmechanism of graphene oxide is proposed. / QC 20100819

<p>This thesis focuses on chaotic stationary waves, both quantum mechanical and classical. In particular we study different statistical properties regarding thesewaves, such as energy transport, intensity (or density) and stress tensor components. Also, the methods used to model these waves are investigated, and somelimitations and specialities are pointed out.</p>

<p>This thesis presents briefly the application of quantum mechanics on systems ofchemical interest, i.e., the field of quantum chemistry and computational chemistry.The molecules of the ten-electron series, hydrogen fluoride, water, ammonia,methane and neon, are taken as computational examples. Some applications ofquantum chemistry are then shown on these systems, with emphasis on the natureof the molecular bonds. Conceptual methods of chemistry and theoreticalchemistry for these systems are shown to be valid with some restrictions, as theseinterpretations does not represent physically measurable entities.The orbitals and orbital energies of neon is studied, the binding van der Waalsinteractionresulting in a Ne2 molecule is studied with a theoretical bond lengthof 3.23 °A and dissociation energy of 81.75 μEh. The equilibrium geometries ofFH, H2O, NH3 and CH4 are studied and the strength and character of the bondsinvolved evaluated using bond order, dipole moment, Mulliken population analysisand L¨owdin population analysis. The concept of electronegativity is studied in thecontext of electron transfer. Lastly, the barrier of inversion for NH3 is studied, withan obtained barrier height of 8.46 mEh and relatively constant electron transfer.</p>