This thesis deals with quantum chemistry methods for large systems. In particular, the thesis focuses on the efficient construction of the Coulomb and exchange matrices which are important parts of the Fock matrix in Hartree-Fock calculations. Density matrix purification, which is a method used to construct the density matrix for a given Fock matrix, is also discussed. The methods described are not only applicable in the Hartree-Fock case, but also in Kohn-Sham Density Functional Theory calculations, where the Coulomb and exchange matrices are parts of the Kohn-Sham matrix. Screening techniques for reducing the computational complexity of both Coulomb and exchange computations are discussed, including the fast multipole method, used for efficient computation of the Coulomb matrix. The thesis also discusses how sparsity in the matrices occurring in Hartree-Fock and Kohn-Sham Density Functional Theory calculations can be used to achieve more efficient storage of matrices as well as more efficient operations on them. / QC 20100817

This thesis presents a theoretical study on optical properties of molecular materials. Special emphasis has been put on the influence of solvent environment, nuclear vibrations, and aggregation effects on molecular properties like linear and nonlinear polarizabilities, one- and two-photon absorption probabilities. All calculations have been performed by means of time independent and dependent quantum chemical methods at the Hartree-Fock and density functional theory levels. Solvation models that include both long range and short range interactions have been employed for calculations of optical properties of molecules in solutions. Pure vibrational and zero-point vibrationally averaged contributions have been taken into account for linear and nonlinear polarizabilities. The linear coupling model is applied to simulate vibronic profiles of optical absorption spectra. The computational strategies described in this thesis are very useful for the design of efficient molecular photonic materials. More specifically, the nonmonotonic behavior of the solvatochromic shifts and the first hyperpolarizability of para-nitroaniline (pNA) with respect to the polarity of the solvents have been theoretically confirmed for the first time. The significant contributions of the hydrogen bonding on the electronic structures of pNA are revealed. Vibrational contributions to the linear and nonlinear polarizabilities of methanol, ethanol and propanol have been calculated both at the static limit and in dynamic optical processes. The importance of vibrational contributions to certain nonlinear optical processes have been demonstrated. A series of end-capped triply branched dendritic chromophores have been studied with the result that their second order nonlinear optical properties are found strongly dependent on the mutual orientations of the three chromophores, numbers of caps and the conjugation length of the chromophores. Several possible mechanisms for the origin of the Q-band splitting of aluminum phthalocyanine chloride have been examined. Calculated vibronic one-photon absorption profiles of two molecular systems are found to be in very good agreement with the corresponding experiments, allowing to provide proper assignments for different spectral features. Furthermore, effects of vibronic coupling in the nonradiative decay processes have been considered which helps to understand the aggregation enhanced luminescence of silole molecules. The study of molecular aggregation effects on two-photon absorption cross sections of octupolar molecules has highlighted the need to use a hybrid method that combines density functional response theory and molecular dynamics simulations for the design of molecular materials. / QC 20100820

The main theme of this thesis is to study effects of different environments on geometric and electronic structures, as well as optical responses, of molecules using time-(in)dependent density functional theory. Theoretical calculations have been carried out for properties that can be measured by conventional and advanced experimental techniques, including one-photon absorption (OPA), two-photon absorption (TPA), surface-enhanced Raman scattering (SERS) and second order nonlinear optical (NLO) response. The obtained good agreement between the theory and the experiment allows to further extract useful information about inter- and intra-molecular interactions that are not accessible experimentally. By comparing calculated one-photon absorption spectra of aluminum phthalocyanine chloride (AlPcCl) and AlPcCl -water complexes with the corresponding experiments, detailed information about the interaction between water molecules and AlPcCl, and geometric changes of AlPcCl molecule has been obtained. Effects of aggregation on two-photon absorption spectra of octupolar molecules have been examined. It is shown that the formation of clusters through inter-molecular hydrogen bonding can drastically change profiles of TPA spectra. It has also demonstrated that a well designed molecular aggregate/cluster, dendrimer, can enhance the second order nonlinear optical response of the molecules. In collaboration with experimentalists, a series of end-capped triply branched dendritic chromophores have been characterized, which can lead to large enhancement of the second order NLO property when the dipoles of the three branches in the dendrimers are highly parallelized. Surface-enhanced Raman scattering has made the detection of single molecules on metal surface become possible. Chemically bonded molecule-metal systems have been extensively studied. We have shown in a joint experimental and theoretical work that stable Raman spectra of a non-bonding molecule, perylene, physically adsorbed on Ag nano-particles can also be observed at low temperature. It is found that the local enhanced field has a tendency to drive molecule toward a gap of two closely lying nano-particles. The trapped molecule can thus provide a stable Raman spectrum with high resolution when its thermal motion is reduced at low temperature. For the ever growing size of molecular complexes, there is always the need to develop new computational methods. A conceptually simple but computationally efficient method, named as central insertion scheme (CIS), is proposed that allows to calculate electronic structure of quasi-periodic system containing more than 100,000 electrons at density functional theory levels. It enables to monitor the evolution of electronic structure with respect to the size of the system. / QC 20100823

This thesis presents theoretical studies of several x-ray spectroscopies - x-ray absorption, x-ray photoelectron emission, radiative and non-radiative resonant Raman scattering spectroscopy. The main focus point is investigating the influence of nuclear dynamics on these spectra for a variety of small molecules - naphthalene, biphenyl, ethylene, the water dimer, HCl, CO. The theoretical tools used consist of the basic equations of the relevant x-ray spectroscopy. Wave packet methods are also used. The molecular parameters needed for our simulations are obtained through suitable quantum chemical calculations, based on either wave function or density functional methods. Our simulations are compared to experimental data, where available. Simulations of x-ray absorption and x-ray photoionization spectra for naphthalene and biphenyl show that the spectral shapes are heavily influenced by the joint effect of two factors -- chemical shifts and excitations of vibrational progression. Comparison between the two molecules and also comparison to a reference case -- benzene, provides useful insight into the molecular behavior under core excitation. In a further step, we consider the O1s x-ray photoelectron spectrum of the water dimer. A substantial broadening of the two bands originating from the donor and the acceptor oxygen is found. It is caused by excitations of soft intermolecular vibrational modes, associated with the hydrogen bond. Another strong influence of the nuclear dynamics is clearly seen in the resonant x-ray Raman scattering of HCl. Vibrational collapse is observed experimentally and confirmed theoretically for distinctive situations. This effect allows to eliminate completely the vibrational broadening, and hence, considerably increase the spectral resolution. We considered also the vibrational dynamics in resonant soft x-ray Raman scattering from ethylene. The importance of vibronic coupling and symmetry effects is discussed and emphasized. We obtained excellent agreement with the experimental data. We predict an interference effect in the resonant Auger scattering from fixed-in-space molecules. By exciting a molecule to a dissociative state and measuring the angular distribution of the Auger electrons in coincidence with the molecular ion, one can observe this effect. The interference pattern can be used after Fourier transformation for extracting structural data about the studied system. We have found that two-center interference leads to an enhancement of the recoil effect. Finally, it is shown that core excitation to doubly-excited dissociative Pi state is accompanied by Doppler splitting of the atomic peak in resonant Auger scattering from carbon monoxide. / QC 20100910

Inter-molecular interactions have significant influences on linear and nonlinear optical properties of molecules including one- and two-photon absorptions, emissions, and various high order nonlinear polarizations. The related investigation has become an active and challenging research area. The theoretical structure-to-property relationship obtained from quantum chemical calculations of single organic conjugated molecules often can not be directly applied to real materials in condensed phases. One has to consider the effect of environment, that is, inter-molecular interactions, where the model systems experience in real experiments or applications. The change of molecular conformations under all kinds of interactions and its effects on linear and nonlinear optical properties are the central issue of this thesis. Special attentions have been paid to symmetrical diamino substituted distyrylbenzene chromophores with different torsional angles, two dipolar merocyanine dyes of various orientations, two isomers of a V-shaped 2-hydroxypyrimidine derivative and their various dimers, and the structural fluctuations of interacting polar chromophores in solutions. Quantum chemical methods in combination with molecular dynamics simulations have been employed to study molecular conformations and optical properties in solutions, in particular the solvent and aggregation effects on one- and two-photon absorption. More specifically, time-dependent density functional theory has been used for all electronic calculations, while the polarizable continuum model and supermolecule approach have also been employed to take into account solvent effects. Moreover, the propagation of an ultrashort laser pulse through a one-dimensional asymmetric organic molecular medium which possesses large permanent dipole moments has been simulated by solving full Maxwell-Bloch equations using predictor-corrector finite-difference time-domain method. We have focused on the supercontinuum generation of spectra and the formation of attosecond pulses. / QC20100630

In his book Wittgenstein on Rules and Private Language (1982) Saul Kripke claims that Wittgenstein argues for a certain form of scepticism in his book Philosophical Investigations (1953), namely a new form of philosophical scepticism, a result of Wittgenstein´s idea of language as language games. Nihilism, scepticism of meaning or of concept, constitutive scepticism are other commentators´ different names of the same phenomenon. The philosophy of Wittgenstein accounts for how our words, including the words of mathematics, have no meaning and there are no a priori justified objective facts as to what I mean about a word. We follow the rules blindly and without justification. We are unable to find any facts against this proposal. Like a ´sceptic´ Wittgenstein denies the ´superlative fact,´ a fact supposed to give an a priori justification to our words. The consensus of a language community is enough to give meaning and assertions to what we in ordinary language call facts, but objective facts in logical meaning a priori, do not exist, a sceptical view in Kripke´s interpretation. Wittgenstein rejects explicit scepticism, but Kripke thinks Wittgenstein did not want to repudiate common belief as a common sense philosopher. This paper ´Wittgenstein and Scepticism´ says that Wittgenstein certainly denies ´superlative fact´, but his reason was founded on conclusions from his investigation of grammar and language, which we use and misuse according to what we want, not to how it is. We demand that logic ought to be absolute, general and consistent, but there is no such logic a priori. Wittgenstein thinks we have to stick to reality and facts of experience. Facts a priori are very convincing facts, but they are not ´sublime´ in a logical metaphysic way. Logic is not rejected and the philosophy of logic uses the same words as common language. Logic has a normative function in our language. We learn words and rules in a certain context and use them in certain situations. How we use the word tells us the meaning of the word and the correct understanding. Our following the rules depends on how they work in real life. / I Wittgenstein on Rules and Private Languages (1982) hävdar Saul Kripke att Wittgensteins resonemang i Filosofiska undersökningar (1953) leder till en speciell  form av skepticism, en filosofisk skepticism, en konsekvens av Wittgensteins uppfattning om språket som språkspel. Nihilism, meningsskepticism, begreppsskepticism, konstitutiv skepticism är andra kommentatorers beteckningar. Wittgensteins filosofi visar att språkets ord, inklusive matematikens ord, saknar mening och inga rättfärdigade objektiva a priori fakta finns om vad jag menar med ett ord. Vi följer språkets regler blint och som det passar oss Argument saknas för att vederlägga  detta påstående. Som en skeptiker förnekar Wittgenstein filosofins "superlative fact", som förmodas ge en a priori grund för vad jag menar med ett ord. En språkgemenskaps konsensus ger dock orden mening och bekräftar vad som i vanligt språk kallas fakta, men objektiva fakta i logisk mening, fakta a priori saknas, d.v.s. en skeptisk uppfattning, enligt Kripkes tolkning Att Wittgenstein själv tar avstånd från skepticismen beror på att han inte vill bryta med den allmänna uppfattningen om fakta och  mening. Uppsatsen "Wittgenstein och skepticismen" visar att visserligen överger Wittgenstein "superlative fact", men detta är ett resultat av hans grammatiska undersökning av språket, vilket vi brukar och missbrukar för våra syften, inte som det är. Vi önskar och fordrar att logiken ger oss ett absolut, generellt och beständigt svar, men ett  sådant svar kan inte logikens a priori ge. Wittgenstein menar att verkligheten och erfarenhetsfakta är vad vi har att hålla oss till. A priori fakta är enligt Wittgenstein mycket övertygande fakta, men inte i den "sublima" logikens metafysiska mening. Logiken förkastas inte, ty logikens filosofi talar inte om ord i någon annan mening än vi gör i det vanliga livet. Logiken har en styrfunktion i språket. Orden lärs in i ett sammanhang och används i ett sammanhang. Användningen av ordet visar om ordets mening är korrekt uppfattad. Vi följer regler efter hur de fungerar i en verklighet

Denna studie fokuserar på konflikthantering och dess egenskaper. Jag har fördjupat mig i praktiska och teoretiska kunskaper i konflikthantering med eleverna. I denna studie kommer jag att intervjua fyra pedagoger, två erfarna lärare och två nyexaminerade pedagoger. Jag kommer också att förklara vilka känslor har för roll i konfliktlösning. Varför jag har valt att skriva om konflikten är på grund av min osäkerhet när det gäller att lösa konflikter med elever så jag har valt att intervjua två erfarna pedagoger. Slutsatsen av min studie är att alla mina fyra informanter anser att den praktiska kunskapen är lika viktig som den teoretiska kunskapen. Studien visar att vi kan få in de olika kunskaper på två olika sätt; genom utbildningen som är den teoretiska kunskapen samt ute i arbetslivet som är den praktiska kunskapen.

Inom kognitionsvetenskapen växer det på flera håll fram konkurrenter till det synsätt på språklig kognition som förespråkats främst av lingvisten Noam Chomsky. Han har argumenterat för att barns förmåga till att snabbt förvärva språks grammatiska komplexitet, beror på att all världens språk delar en underliggande universell grammatik som finns inkodad i människohjärnan från födseln. Enligt denna syn betraktas grammatik som ett abstrakt regelstyrt system, slutet och utan direkt påverkan från omgivningen. Efterföljande forskning har kommit att visa på många svårigheter för denna hypotes, varvid alternativa ansatser har trätt fram. Som ett resultat försöker många forskare numera istället förklara färdigheter i grammatik som en förlängning av kognitiva och kommunikativa förmågor. Uppsatsen ger en kort bakgrund om Chomskys idéer och hur han resonerade sig fram till sin hypotes. Via en rad olika överväganden utifrån empiriska observationer och experiment, och på området nyutvecklad teori, söks därmed andra förklaringsvägar. Uppsatsen undersöker ett antal implikationer och hur de påverkar forskningen kring språkförmågan.

Syftet med denna studie är att undersöka om gymnasieutbildningen inom Hotell- och restaurangprogrammet lever upp till restaurangbranschens förväntningar. Avsikten med arbetet är även att ta reda på hur samarbetet mellan skola och arbetsliv fungerar samt vilka kunskaper som eleven förväntas ha efter avslutad utbildning. Dessutom vill vi veta vilka egenskaper som har relevans för anställningsbarheten.   Läroplanen (Lpf 94) säger att skolan ska eftersträva ett bra samarbete med arbetslivet och att eleven bör få kännedom om arbetslivets villkor. I programmålen för de yrkesförberedande programmen står att den arbetsplatsförlagda utbildningen har en central betydelse där grunderna ges i skolan och där det förväntas att specifika yrkeskunskaper vidareutvecklas i arbetslivet. Genom en inblick i arbetslivet får eleven kunskap om yrkespraxis och yrkeskultur där färdigheter tränas och förståelsen för yrket utvecklas.   Studien är av empirisk karaktär där vi har intervjuat branschrepresentanter och karaktärsämneslärare. Resultatet visar att branschens förväntningar inte införlivas, då eleven efter avslutad utbildning sällan är anställningsbar. Vidare visar studien att både skola och bransch anser att grundkunskaper är viktiga men egenskaper som visat intresse, samarbetsförmåga och social kompetens påverkar anställningsbarheten. Dessutom framkommer att samarbetet mellan de båda kunskapskulturerna måste förbättras.

<p>A theoretical framework for calculating electron transport through molecular junctions is presented. It is based on scattering theory using a Green's function formalism. The model can take both elastic and inelastic scattering into account and treats chemical and physical bonds on equal footing. It is shown that it is quite reliable with respect to the choice of functional and basis set. Applications concerning both elastic and inelastic transport are presented, though the emphasis is on the inelastic transport properties. The elastic scattering application part is divided in two part. The first part demonstrates how the current magnitude is strongly related to the junction width, which provides an explanation why experimentalists get two orders of magnitude differences when performing measurements on the same type of system. The second part is devoted to a study of how hydrogenbonding affects the current-voltage (I-V) characteristics. It is shown that for a conjugated molecule with functional groups, the effects can be quite dramatic. This shows the importance of taking possible intermolecular interactions into account when evaluating and comparing experimental data. The inelastic scattering part is devoted to get accurate predictions of inelastic electron tunneling spectroscopy (IETS) experiments. The emphasis has been on elucidating the importance of various bonding conditions for the IETS. It is shown that the IETS is very sensitive to the shape of the electrodes and it can also be used to discriminate between different intramolecular conformations. Temperature dependence is nicely reproduced. The junction width is shown to be of importance and comparisons between experiment as well as other theoretical predictions are made.</p>