Method specific Cholesky decomposition : Coulomb and exchange energies

We present a novel approach to the calculation of the Coulomb and exchange contributions to the total electronic energy in self consistent field and density functional theory. The numerical procedure is based on the Cholesky decomposition and involves decomposition of specific Hadamard product matrices that enter the energy expression. In this way, we determine an auxiliary basis and obtain a dramatic reduction in size as compared to the resolution of identity (RI) method. Although the auxiliary basis is determined from the energy expression, we have complete control of the errors in the gradient or Fock matrix. Another important advantage of this method specific Cholesky decomposition is that the exchange energy and Fock matrix can be evaluated with a linear scaling effort contrary to the RI method or standard Cholesky decomposition of the two-electron integral matrix. The methods presented show the same scaling properties as the so-called local density fitting methods, but with full error [email protected]

Militära Fantasier: Njutande och fantasi i militär fitness

Uppsatsen avhandlar ett samtida växande fenomen som samlar miljoner deltagare världen över, militär fitness. I arbetet har jag undersökt militära fitnessarrangemang med syfte att förstå hur de organiserar deltagare och åskådares njutningar och hur dessa struktureras av den militära närvaron. Utifrån mitt material och den lacanska teorin formulerar jag en förståelse av militarism som ett särskilt sätt att njuta av militären. Detta njutande, djupare än argument, visar jag drar det civila närmre det militära genom arrangemang som militär fitness

Framgång och Förfall: En sociologisk undersökning av förändring och konflikt i Vellinge tätort.

The following thesis examines two responses to processes of social change within the small town of Vellinge in the province of Scania, Sweden. The experiences of change within the town appear in the guise of two contradicting narratives – one of the town’s progress and the other of its decline – which I aim to approximate from nine in-depth interviews with eight inhabitants conducted in two cycles. In this study I explore how citizens of the town make sense of their town, its history and their own history within it, while also relating such constructions to the demographic, economic and social vicissitudes within town. Working within a Marxist framework, the narrative of Vellinge’s progress and the one of Vellinge’s decline seem to display a conflict between classes in town while still unable to conceive it as such – resulting in the conflict’s disavowal and externalization onto a foreign intruder. One of my main findings during my research was that not all disorder and vice were able to induce experiences of disruption among the inhabitants. Some disorder, herein conceptualized as non-antagonistic seemed internalized into the social order itself, making it a form of ‘ordered disorderliness’. Whereas another kind of disorder, imagined stemming from a foreign intruder, produced deep experiences of social unease and disruption. It was regarded as antagonistic disorder.Vi lever idag i en tid av fundamental osäkerhet och striden får vi inte sällan höra står mellan de som går en osäker framtid till mötes och de som nostalgiskt blickar tillbaka. I Vellinge möter vi de som med vemod ser sin ort förändras till vad den inte tycks ha varit förut, liksom de som betraktar ortens utveckling i starkt positiva ordalag. Men vi möter också personer med olika materiella förutsättningar där, men sällan talar någon om detta. I föreliggande arbete har jag undersökt hur nio invånare i Vellinge berättar om sin orts historia, tillstånd och framtid. Det visar sig snabbt att orten inte kan begripas utan hänsyn till grannstaden Malmö, för att länge tycks orten ha organiserat sig som dess motpol till vad som beskrivs som ett litet ’reservat’. I takt med att flyktinginvandringen till Malmö har ökat och staden tett sig alltmera stökig och osäker har det lilla Vellingereservatets anseende ökat och mer och mer har den lilla orten framstått som en trygg tillflyktsort undan oordning och stök. I takt med att allt fler sett sig manade att fly den oordnade tillvaron i Malmö har bostadspriserna stegrat på ett explosionsartat sett som vidare skiktat bygemenskapen i två delar med högst olikartade förutsättningar i orten. I synnerhet de lägre klasserna upplever därav sin orts förfall, medan de övre (ofta nyinflyttade) snarare upplever dess framgång. I orten uttrycks däremot aldrig denna konflikt omedelbart som en konflikt mellan klasser, utan istället förskjuts konflikten till en Inkräktare som framstår som orsak till att motsättningarna i orten har exploderat

On the growth kinetics, texture, microstructure, and mechanical properties of tungsten carbonitride deposited by chemical vapor deposition

Tungsten carbonitride [W(C,N)] was deposited on cemented carbide substrates by chemical vapor deposition (CVD) in a hot-wall reactor using tungsten hexafluoride (WF6), acetonitrile (CH3CN), and hydrogen (H-2) as precursors. Tungsten carbides and nitrides with a hexagonal 6-WC type structure are generally difficult to obtain by CVD. Here, it was found that the combination of WF6 and CH3CN precursors enabled the deposition of W(C,N) coatings with a delta-WC type structure and columnar grains. A process window as a function of the deposition temperature and precursor partial pressures was determined to establish the conditions for the deposition of such coatings. Scanning electron microscopy, x-ray diffraction, electron backscatter diffraction, and elastic recoil detection analysis were used for the investigation of the coating thickness, microstructure, texture, and composition. From the investigation of the kinetics, it was concluded that the growth was mainly controlled by surface kinetics with an apparent activation energy of 77 kJ/mol, yielding an excellent step coverage. The partial reaction orders of the reactants together with their influence on the microstructure and coating composition was further used to gain a deeper understanding of the growth mechanism. Within the process window, the microstructure and the texture of the W(C,N) coatings could be tailored by the process parameters, enabling microstructural engineering with tuning of the mechanical properties of the W(C,N) coatings. The nanoindentation hardness (36.6-45.7 GPa) and elastic modulus (564-761 GPa) were found to be closely related to the microstructure

Chemical vapor deposition of TiN on transition metal substrates

The growth of chemical vapor deposited TiN from a reaction gas mixture of TiCl4, N-2 and H-2 was investigated on three different transition metal substrates: Fe, Co and Ni at deposition temperatures ranging from 850 degrees C to 950 degrees C. The interactions between the substrate metals and the gas phase were investigated using thermodynamic calculations. The TiN coatings were characterized by scanning electron microscopy, scanning transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and transmission Kikuchi diffraction. Chemical vapor deposition (CVD) of TiN on Co substrates resulted in dense, columnar coatings of single phase TiN. The activation energy for TiN deposition on Co was determined to be 90 kJ/mol. CVD of TiN on Fe substrates caused severe substrate corrosion by the formation of gaseous FeClx. Due to the substrate corrosion, the activation energy could not be determined. Furthermore, it was found that CVD of TiN on Ni substrates produced a phase mixture of TiN and Ni3Ti. Formation of Ni3Ti could be minimized by decreasing the H-2 partial pressure and increasing the N-2 partial pressure. Deposition on Ni yielded two different activation energies, 40 kJ/mol in the temperature interval 850 degrees C to 900 degrees C and 165 kJ/mol in the interval 900 degrees C to 950 degrees C. This is an indication of two different types of process control, which were identified as Ni diffusion into the growing film and a gas phase processes. The results of the present study showed that CVD of TiN on a cemented carbide using Fe and Ni in the binder phase, must be optimized in order to avoid corrosion or unwanted phases. Methods to achieve this are presented in this paper

Tribological properties of highly oriented Ti(C,N) deposited by chemical vapor deposition

Two Ti(C,N) coatings were tested by means of micro abrasion and scratch testing. The coatings differed in grain size, orientation (<111> and <111>, <311> and <211> respectively) and hardness (36 GPa and 23 GPa respectively). The <111> oriented coating had a 20% higher wear resistance compared to the reference coating when abraded with 1 pm diamonds. When abraded with 6 pm diamonds the abrasion resistance of the reference coating was superior compared to the <111> oriented coating by 36%. Furthermore, it was found that the <111> oriented coating had 35% better adhesion compared to the reference. The improved mechanical properties of the <111> oriented coating was attributed to a high degree of orientation and the higher hardness

On the growth, orientation and hardness of chemical vapor deposited Ti(C,N)

Chemical vapor deposition (CVD) of Ti(C,N) from a reaction gas mixture of TiCl4, CH3CN, H2 and N2 was investigated with respect to gas phase composition and kinetics. The gas phase composition was modelled by thermodynamic calculations and the growth rate of the CVD process was measured when replacing H2 for N2 while the sum of partial pressures H2+N2 was kept constant. The N2/H2 molar ratio was varied from 0 to 19. Single crystal c-sapphire was used as substrates. It was found that low molar ratios (N2/H2 molar ratio below 0.6) lead to an increased Ti(C,N) growth rate with up to 22%, compared to deposition without added N2. The mechanism responsible for the increased growth rate was attributed to the formation and increased gas phase concentration of one major growth species, HCN, in the gas phase. The texture of the Ti(C,N) films were also studied. ⟨211⟩ textured layers were deposited at N2/H2 molar ratios below 9. At higher molar ratios, ⟨111⟩ oriented Ti(C,N) layers were deposited and the grain size increased considerably. The films deposited at a N2/H2 ratio above 9 exhibited superior hardness, reaching 37GPa. The increased hardness is attributed to an almost epitaxial orientation between the layer and the substrate. The absence of grain twinning in the ⟨111⟩ oriented layer also contributed to the increased hardness.The Ti(C,N) layers were characterized by elastic recoil detection analysis, X-ray photo electron spectroscopy, scanning electron microscopy, X-ray diffraction and nanoindentation

Cholesky decomposition-based definition of atomic subsystems in electronic structure calculations

Decomposing the Hartree-Fock one-electron density matrix and a virtual pseudodensity matrix, we obtain an orthogonal set of normalized molecular orbitals with local character to be used in post-Hartree-Fock calculations. The applicability of the procedure is illustrated by calculating CCSD(T) energies and CCSD molecular properties in reduced active spaces. \uc2\ua9 2010 American Institute of Physics

Chemical vapor deposition of TiN on a CoCrFeNi multi-principal element alloy substrate

The reactivity of a quaternary multi-principal element alloy (MPEA), CoCrFeNi, as a substrate in thermal halide chemical vapor deposition (CVD) processes for titanium nitride (TiN) coatings was studied. The coatings were deposited at 850 degrees C-950 degrees C using TiCl4, H-2 and N-2 precursors. The coating microstructures were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM) with energy dispersive X-ray spectroscopy (EDS). Thermodynamic calculations of substrate and coating stability for a gas phase environment of N-2 and H-2 within a temperature range relevant for the experiments showed that Cr is expected to form hexagonal Cr2N and cubic (Ti1-epsilon 1 Cr epsilon 1)N or (Cr1-epsilon 2 Ti epsilon 2)N phases. These phases could however not be discerned in the samples by XRD after the depositions. Cr was detected at the grain boundaries and the top surface by EDS for a sample synthesized at 950 degrees C. Grain boundary and surface diffusion, respectively, were the suggested mechanisms for Cr transport into the coating and onto the top surface. Although thermodynamic calculations indicated that Cr is the most easily etched component of the CoCrFeNi alloy to form gaseous chlorides in similar concentrations to that of the residual Ti-chlorides, no sign of etching were found according to the imaging of the sample cross-sections using SEM and TEM. Cross-section and top surface images further confirmed that the choice of substrate had no significant detrimental influence on the film growth or microstructure