Utjecaj ostatka molekule na apsorpcijsku frekvenciju karbonilne skupine kinona

Elektronski utjecaji ostatka molekule na quasi-karakteristiene frekvencije u bliskom infracrvenom podrucju ili su elektrostatiene prirode ili se sastoje u promjeni hibridizacije. U seriji kinona usporedena je frekvencija karbonila s redoks-potencijalom i s razlikom energije rezonancije kinona i odnosnog hidrokinona. Kod metalnih derivata oksikinona objasnjava se jako pomicanje karbonilnog apsorpcijskog podrucja analogijom s karboksilat-ionom

Intramolecular Hydrogen Bonding in Guanidinium and Potassium Hydrogen Malonates - an Infrared and X-Ray Diffraction Study

A new modification of potassium hydrogen malonate was obtained by crystallization from dimethylsulphoxide (DMSO)\u27 solution. Its infrared spectrum differs in its essential features from the spectra of the known modification crystallizing from water!-" but resemble those of guanidinium hydrogen malonate. Both spectra are interpreted in terms of strong, intramolecular hydrogen bonding, This is supported by the fact that the main features (CO and OH stretching) remain essentially unchanged on dissolution in DMSO and by the X-ray diffraction on guanidinium hydrogen malonate. The structure of its crystals was solved by the direct method and refined by full matrix least squares to R value of 0.044 for 453 observed reflections. The structure consists of planar guanidinium ions and hydrogen maleate residues containing short intramolecular, but asymmetric bonds of 2.407(3)A

Assessment of Liquefaction Potential Relevant to Choice of Type and Depth of Foundations in Seismically Active Areas

There is evidence of great increase of pore pressures in saturated sand soils during cyclic loading caused by earthquakes. These increased pore pressures can often increase to effective stresses in soil. Dependant on sand density, this can lead to a total loss of shear strength, liquefaction or greater deformability of soil. Emergence of liquefaction or great deformations within soil can cause significant damage or total destruction of constructions on the ground, even when they have been correctly designed. For this reason, it is very important to perform detailed geotechnical and seismic investigations of ground conditions and evaluate liquefaction potential for saturated sand soil in seismically active terrain. It is not possible to design stable constructions in certain types of terrain without the analyses of liquefaction potential. This paper refers to the comparative cost-analyses of two possible ways of the foundations of the business complex: shallow foundations with stabilization of potentially liquefiable sand deposit using vertical gravel drains versus deep pile foundation on unliquefiable soil

The Electrocrystallization of Metals. Investigation of Zinc

In electrodeposition of zinc depending on the condition of deposition, various effects of electrocrystallization can be observed. In acid solution of zinc sulfate the considerable surface diffusion overpotential appears at lower values of the total overpotential, indicating the surface diffusion of actions as the rate determining step. An interesting dependence of exchange current density on pH with a minimum at pH - 2 indicate the probable change in structure of the reacting particle. The mechanism of the reaction is evaluated. In alkaline zincate solutions no surface diffusion limitations can be detected. However, due to the rather low zincate ion concentration and high exchange current density zinc deposition proceeds practically always under the diffusion control. Morphology of zinc deposited depends considerably on the value of the electrode potential. This can be seen from the experiments in which the deposition morphology was observed with a scanning electron microscope. It was found possible to disrupt the deposition repeatedly for microscopic observation and than continue deposition. At low overpotentials (up to 50 mV) epitaxial layer type growth was observed with the linear increase of the microstep width with time. For this effect a theory is proposed which accounts also for the observed effects of substrate orientation. At larger overpotentials (50-100 mV) boulder type deposit was observed, most of which were not epitaxial with the substrate. They are suggested to be originated by nucleation. The boulder density per cm2 is first sharply increasing, and then slowly decreasing with time. A statistical calculation for this is given based on the model that large boulders consume the smaller ones. With further deposition a small fraction of the boulders develop into dendrites, their number being limited by the available total current

Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains

We study the quasiparticle band structure of isolated, infinite HF and HCl bent (zigzag) chains and examine the effect of the crystal field on the energy levels of the constituent monomers. The chains are one of the simplest but realistic models of the corresponding three-dimensional crystalline solids. To describe the isolated monomers and the chains, we set out from the Hartree-Fock approximation, harnessing the advanced Green's function methods "local molecular orbital algebraic diagrammatic construction" (ADC) scheme and "local crystal orbital ADC" (CO-ADC) in a strict second order approximation, ADC(2,2) and CO-ADC(2,2), respectively, to account for electron correlations. The configuration space of the periodic correlation calculations is found to converge rapidly only requiring nearest-neighbor contributions to be regarded. Although electron correlations cause a pronounced shift of the quasiparticle band structure of the chains with respect to the Hartree-Fock result, the bandwidth essentially remains unaltered in contrast to, e.g., covalently bound compounds.Comment: 11 pages, 6 figures, 6 tables, RevTeX4, corrected typoe

Evidence of Polaron Excitations in Low Temperature Raman Spectra of Oxalic Acid Dihydrate

Low temperature Raman spectra of oxalic acid dihydrate (8K - 300 K) both for polycrystalline and single crystal phase show strong variation with temperature in the interval from 1200 to 2000 cm-1. Previous low temperature diffraction studies all confirmed the stability of the crystal P21/n phase with no indications of any phase transition, reporting the existence of a strong hydrogen bond between the oxalic acid and a water molecule. A new group of Raman bands in the 1200 – 1300 cm-1 interval below 90 K is observed, caused by possible loss of the centre of inversion. This in turn could originate either due to disorder in hydroxyl proton positions, or due to proton transfer from carboxylic group to water molecule. The hypothesis of proton transfer is further supported by the emergence of new bands centered at 1600 cm-1 and 1813 cm-1, which can be explained with vibrations of H3O+ ions. The broad band at 1600 cm-1 looses intensity, while the band at 1813 cm-1 gains intensity on cooling. The agreement between quantum calculations of vibrational spectra and experimentally observed Raman bands of hydronium ions in oxalic acid sesquihydrate crystal corroborate this hypothesis