A recently developed density-functional method based on localized densities is applied to calculate electronic, structural, and vibrational properties of 20 alkali halides with elements lithium through cesium and fluorine through iodine. Properties calculated include dissociation energy, lattice parameter, dielectric constant, elastic moduli, and phonon frequencies for the high-symmetry points of the Brillouin zone. Results are discussed and compared with experiment and other calculations.
We present a density functional method which expresses the charge density of a system of atoms as a sum over localized atomiclike densities derived from potentials defined variationally from the total energy expression, which includes contributions from overlapping densities. An approach for systematically increasing the variational freedom of the atomiclike densities is introduced and tested for the water molecule. For the water molecule our method results in complete charge transfer for sufficiently small bond lengths and reverses the charge transfer at large bond lengths. In case of complete charge transfer the overlap contributions are zero, allowing a direct comparison with the traditional Kohn-Sham approach.
Structure of the nitride-oxide surface layers, formed using glow discharge technique at low temperature (between 200 and 380°C) changing the parameters of the process, was examined applying X-ray diffraction as well as transmission electron microscopy. The phase analysis was supported by results obtained from XPS measurement. Obtained results have shown that low temperature nitriding/oxiding produced the thin layers (18 ÷ 30 nm in thickness), which consist of titanium nitride and oxide phase. Low amount of the nickel-titanium oxide was also identified in the layer produced at higher temperature. Decrease of nitriding/oxidizing temperature below 300oC cause that between nitride-oxide surface layer and NiTi alloy did not create the intermediate layer of Ni3Ti phase. The results were verified and confirmed by observation carried out using high resolution electron microscopy. The corrosion properties of such coatings were tested in the physiological Tyrod’s solution using the cyclic potentiodynamic polarization method.
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