Review on Standardisation of Methods Characterising the Geometric Structure of Dispersed or Porous Solids

Short survey on the latest developments on standardisation and standard reference materials for particles, surfaces and pore size analysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Binding energy of metals in pseudo-ion approximation

On the basis of pseudopotential theory we obtain a simple expression for the interaction energy between ions in a metallic system replacing the ion form factor in the direct (Coulomb) interaction by the pseudo-ion form factor of the indirect (conduction mediated) interaction. This substitution can be justified for non-overlapping radially symmetric rigid ions. For the pseudo-ion form factor (which includes ionic and orthogonalization effects) a model function is proposed and the model parameters are determined for lithium, sodium, potassium, rubidium and aluminium by fitting to experimental phonon dispersion curves. Using these form factors and an appropriate dielectric function we proceed to calculate binding energies. One finds that the values obtained show a remarkable agreement with experimental results. This suggests that the proposed reduced expression for the interaction energy and its numerical determination from experimental phonon curves is a good approximation method in evaluating and understanding the binding energy of a metal.     

Die optischen Eigenschaften dielektrischer Schichten mit kleinen Homogenitätsstörungen

The reflectivity near the polarizing angle is being calculated both for slightly non-homogeneous dielectric films (possessing small gradients in the refractive index) and also for double layers having slightly different refractive indices. Thus discrepancies can be removed which may arise, when the refractive indices are determined from the Brewster angle, and it was also possible to work out a procedure which permits to analyse the structure of the various layers from experimentally obtained spectral reflectivity curves near the Brewster angle.     

Die Kristallstruktur von Zirkoniumtetrachlorid

Zirconium(IV) chloride crystallizes in the monoclinic space group P2/c with a = 6.361, b = 7.407, c = 6.256 Å β = 109.30°, Z = 2. The single crystal X-ray structure analysis shows the structure to consist of an arrangement of [ZrCl_4/2Cl₂] zig-zag chains. Within the chains each Zr atom has an octahedral environment; the octahedra are linked through sharing edges, the two terminal Cl ligands being mutually in cis-position. The structure is closely related to those of TcCl₄, PtI₄ and MoOCl₃. The Zr? Cl bond lengths are 2.655 (bridge), 2.498 (bridge) and 2.307 Å (terminal) ZrBr₄, HfCl₄, and HfBr₄ are isostructural with ZrCl₄     

Nuclear Spin Orientation Created in Heavy Ion Collisions and the Sign of the Q Moment of 13B

The momentum dependences of the nuclear spin polarization P and alignment A of ¹³B(, T _1/2 = 17.36 ms) produced in the 100A MeV ¹⁵N + Be collisions have been measured by detecting β-ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some relaxation mechanisms must be take into account. Comparing the signs of the observed alignment of ¹²B, the sign of the quadrupole coupling constant eqQ of ¹³B in TiO₂ was determined to be positive.