Structures of zinc selenite and copper selenite
Les deux composes cristallisent dans le systeme orthorhombique, groupe PcaB. Coordination bipyramidale rhomboedrique et pyramidale rhomboedrique autour de En et Cu respectivement
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Spin reorientation in NdDyFe14B
NdDyFe14B shows a spin reorientation around TS =92 K which is lower than that obtained for Nd2Fe14B (150 K). Neutron diffraction on powder specimen indicates a preferential occupation for Dy atoms of the 4 f sites, but does not reveal the spin reorientation.
Angle-resolved x-ray photoemission from the valence bands of tungsten with high angular resolution and temperature variation
Angle-resolved valence photoemission spectra have been obtained for W(011) and W(001) using Al K\ensuremath{\alpha} and Mg K\ensuremath{\alpha} excitation and with both normal and off-normal emission directions. The angular resolution was \ensuremath{\lesssim}\ifmmode\pm\else\textpm\fi{}1.0\ifmmode^\circ\else\textdegr…
Porphyrins
Initial steps in the photodissociation of nitrosyl ferrous and ferric heme complexes have been investigated by calculation of the ground and excited states and electronic spectra as a function of iron-ligand bond lengthening. The method used is an all valence semi empirical INDO-SCF-CI procedure with transition metal…
A b i n i t i o SCF-CI calculation on free base porphin and chlorin; theoretical analysis on intensities of the absorption spectra
A b initio self-consistent field and configuration interaction (SCF-CI) calculations with a minimal basis set are carried out on a few lower π→π* states of free base porphin and free base chlorin. Excitation energies and oscillator strength of these states are calculated and are compared with observed values. For the…
Epitaxial growth and the crystallographic, dielectric, and pyroelectric properties of lanthanum-modified lead titanate thin films
Using an rf-magnetron sputtering method, highly c-axis-oriented La-modified PbTiO3 (PLT) thin films with compositions of Pb1−xLaxTi1−x/4O3, where x=0.05, 0.10, and 0.15, have been obtained on MgO single-crystal and epitaxial Pt thin-film substrates under conditions of low gas pressure and low deposition rate. The degr…
Broadband near-infrared luminescence of Cr+3 in the elpasolite lattices Cs2NaInCl6, Cs2NaYCl6, and Cs2NaYBr6
The broadband luminescence of isolated Cr+3 ions in the title lattices is investigated. The 4T2g lowest excited state is found to undergo Jahn–Teller distortion in the eg coordinate, in addition to expanding along the a1g. Quantitative determination of these displacements is made by analysis of extremely rich fine str…
Positron-annihilation study of the half-metallic ferromagnet NiMnSb: Theory
Calculations of the electronic structure, the Fermi surface, and the momentum density of annihilation photon pairs are presented in preparation for an experimental study of the half-metallic ferromagnet NiMnSb with the aid of the two-dimensional angular correlation of annihilation radiation technique. The band structu…
Thermodynamics of polymer solutions
The free energy of a polmyer solution is derived by a consideration of the monomer density fluctuations and incorporating three-body interactions. Explicit interpolation formulas are obtained for the concentration dependence of the correlation length for arbitrary strengths of two- and three-body interactions within t…
Phonon localization in glasses
A universal but unexplained characteristic of glasses is the temperature-independent region or plateau in the thermal conductivity for temperatures 1--30 K. Examination of low-temperature thermal conductivity data for a wide variety of glasses indicates that the mean free path of the average thermal phonon becomes les…
Thermal conductivity of amorphous solids
The thermal conductivities of glassy solids, when scaled by material parameters, have a similar magnitude and temperature dependence, from the lowest temperatures yet measured, to the melt. Both empirical results and theoretical models are reviewed briefly. It is emphasized that the thermal conductivity of an amorphou…
Low-frequency modes in vitreous silica
Measurements of the elastic and inelastic neutron scattering from vitreous silica in the frequency range 0.3 to 4 THz and with scattering vectors in the range 0.2 to 5.3 A${\r{}}^{\mathrm{\ensuremath{-}}1}$ are analyzed in conjunction with heat-capacity measurements on the same samples to provide a microscopic descrip…
Towards organic polymers with very small intrinsic band gaps. I. Electronic structure of polyisothianaphthene and derivatives
We present valence effective Hamiltonian (VEH) band-structure calculations on polyisothianaphthene and some of its simple derivatives. Our goal is to rationalize the lowering of the band gap by about 1 eV which is experimentally observed in polyisothianaphthene (Eg=∼1 eV) relative to the parent polymer, polythiophene…
Lattice thermal conductivity: A comparison of molecular dynamics and anharmonic lattice dynamics
The thermal conductivity of a monatomic face-centered-cubic lattice has been calculated over a range of temperatures from one-twentieth to one-half the melting temperature. An inverse-twelfth-power ``soft-sphere'' potential was used to represent the interatomic forces. We have examined, quantitatively, the approximati…
Piezoelectricity and flexoelectricity in crystalline dielectrics
Piezoelectricity in pyroelectrics and the linear response of polarization to a strain gradient?lexoelectricity) are discussed in the framework of the unified approach. It was pointed out by Born and Huang and by Martin, that there was a difference between the piezoelectric response for the cases of a sound wave and of…
How Organic Coating Systems Protect Against Corrosion
The electrochemical, physicochemical and adhesional aspects of corrosion protection by organic coatings are shortly discussed. Attention is drawn to some inconsistancies in the interpretation of protective mechanisms and suggestions are given how protective principles may be optimally realized in practical systems.
Polymeric Materials for Corrosion Control: An Overview
Polymeric materials are widely used to control the corrosion of metals, both to maintain appearance and to prevent loss of structural integrity. In this chapter, the fundamentals of metallic corrosion are briefly reviewed. Methods of studying corrosion, and of evaluating the performance of polymeric materials used in…
Mechanisms of De-adhesion of Organic Coatings from Metal Surfaces
Organic coatings lose adherence to a metal substrate by many processes. The eventual consequence of this de-adhesion is corrosion of the metal beneath the coating. Among the important de-adhesion processes are: loss of adhesion when wet, cathodic delamination, cathodic blistering, swelling of the polymer, gas blisteri…
Polymeric Materials for Corrosion Control
Polymeric materials are widely used to control the corrosion of metals, both to maintain appearance and to prevent loss of structural integrity. In this chapter, the fundamentals of metallic corrosion are briefly reviewed. Methods of studying corrosion, and of evaluating the performance of polymeric materials used in…
Optical Constants Of Thin Silver And Titanium Nitride Films
The optical constants of thin films of silver and titanium nitride have been obtained in the visible and near infrared spectral regions by the Nestell-Christy method. The silver films, 9-.27 nm thick, were prepared by d.c. magnetron sputtering at low pressures. It is found that the silver films, prepared at sputtering…