Spin polarization in low-energy electron diffraction: Surface analysis of Pt(111)

Transverse and longitudinal spin polarization components arising in the diffraction of unpolarized low-energy electrons from Pt(111) have been studied as functions of energy and diffraction geometry. Experimental data measured by means of a Mott detector are in good agreement with theoretical results obtained by relativistic LEED calculations. A detailed investigation of the selective sensitivity of the calculated polarization profiles to the surface relaxation δ₁₂ and to various non-structural model features firstly supports an ion-core potential involving an energy-dependent exchange approximation (by discriminating against two band structure potentials), and secondly establishes the geometry of Pt(111) as unreconstructed with a possible slight outward relaxation of the topmost atomic layer (δ₁₂ = 0.5% ± 1.0% of the bulk interlayer distance). A surface Debye temperature is found close to the bulk value 230 K.     

Novel correlation of Schottky constants with lattice energies for II-VI and I-VII compounds

Correlations of computed Schottky constants () with structural and thermodynamic properties showed linear dependences of log K_S on the lattice energies for the Zn-, Cd-, Hg-, Mg-, and Sr-chalcogenides and for the Na- and K-halides. These findings suggest a basic relation between the Schottky constants and the lattice energies for these families of compounds from different parts of the Periodic Table, namely, =−(2.303nRT log K_S)+2.303nRm_b+2.303nRTi_b. is the experimental (Born-Haber) lattice energy (enthalpy), n is a constant approximately equal to the formal valence (charge) of the material, m_b and i_b are the slope and intercept, respectively, of the intercept b (of the log K_S versus linear relation) versus the reciprocal temperature. The results of this work also provide an empirical correlation between the Gibbs free energy of vacancy formation and the lattice energy.     

Asymptotic electromagnetic fields in non-relativistic QED: The problem of existence revisited

This paper is devoted to the scattering of photons by charged particles in models of non-relativistic quantum mechanical matter coupled minimally to the soft modes of the quantized electromagnetic field. We prove existence of scattering states involving an arbitrary number of asymptotic photons of arbitrarily high energy. Previously, upper bounds on the photon energies seemed necessary in the case of n>1 asymptotic photons and non-confined, non-relativistic charged particles.     

Building-integrated PV activities within the IEA framework: Going from task 16 to task VII

Early in 1997 a new task will be launched within the scope of the International Energy Agency (IEA) Photovoltaic Power Systems Implementing Agreement. This new task, Task VII, aims to develop building-integrated photovoltaic (BIPV) technology, consider ing technical viability, economics and aesthetic quality. The task concentrates strongly on the involvement of architects, building engineers and urban planners, and the ability to increase their interest in BIPV. Task VII succeeds Task 16, ‘Photovoltaics in Buildings’ of the IEA Solar Heating and Cooling Program, completed in March 1996. It has proved to be very effective in developing and demonstrating new concepts for building-integrated photovoltaics, with t he international cooperation in the task assisting in advancing and promoting the application of photovoltaics in both residential and commercial buildings. Task 16 played a pioneering role in obtaining the World's attention for BIPV. It is expected that Task VII will provide accelerated development and market acceptance of this promising technology.