A simple form of multi-ion interaction has been constructed for the purpose of atomistic simulation of transition metals. The model energy consists of a bonding term, which is the square-root of a site density ρi, summed over atoms i, and a repulsive pairwise term of the form The site density ρi is defined as sum over neighbouring sites j of a cohesive potential (R ij). Both V and are assumed to be short-ranged and are parameterized to fit the lattice constant, cohesive energy and elastic moduli of the seven body-centred-cubic (b.c.c.) transition metals. The result is a simple model which, unlike a pair-potential model, can account for experimental vacancy-formation energies and does not require an externally applied pressure to balance the “Cauchy pressure”.

A simple empirical N-body potential for transition metals

A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Stability/degradation of polymer solar cells

Atomic-level structure and structure–property relationship in metallic glasses

The elastic properties, elastic models and elastic perspectives of metallic glasses

Positron-annihilation $S$-parameter measurements in thermal equilibrium on pure and carbon-doped (50 and 750 at. ppm) $\ensuremath{\alpha}$-iron are presented. It is shown that trapping of positrons in both monovacancies and carbon-vacancy pairs occurs, even far above the dissociation temperature of the vacancy pairs. Therefore, a three-state trapping model is used in the analysis of the measured $S$ curves. The vacancy-formation enthalpy in both the paramagnetic and ferromagnetic state is deduced: It is found to be 1.79 \ifmmode\pm\else\textpm\fi{} 0.10 eV in the paramagnetic state and 2.0 \ifmmode\pm\else\textpm\fi{} 0.2 eV in the ferromagnetic state. These values are larger than those published so far. The activation enthalpy for vacancy migration obtained by combining the values cited above with recently published self-diffusion enthalpy values confirms the applicability of the one-interstitial model in $\ensuremath{\alpha}$-iron.

Positron annihilation on pure and carbon-doped α-iron in thermal equilibrium

A quantitative model for the evolution from random orientation to a unique texture in PVD thin film growth

Oxidational wear of TiN coatings on tool steel and nitrided tool steel in unlubricated fretting

Adhesion of diamond coatings on cemented carbides

Photothermal deflection spectroscopy (PDS) is used to study subgap optical absorption in chemical vapor deposited (CVD) diamond films. The high PDS sensitivity over a broad investigated spectral range enabled the investigation of the main defect structure in CVD diamond upon changing the deposition conditions. All films exhibit a very characteristic shape of the subgap optical absorption in the infrared and visible spectral regions, which scales with the content of amorphous carbon phase in grain boundaries. In best-quality films the character of the fundamental absorption edge is attained and the subgap absorption reduced. For nanocrystalline approaching films, an absorption spectrum resembling closely the one for amorphous carbon (a-C:H) films is observed. Based on these results a mathematical model for the description of the optical absorption coefficient in the subgap region is developed. A numerical deconvolution procedure is applied to fit the experimental data. \textcopyright{} 1996 The American Physical Society.

Lambert Stals

Papers

Positron annihilation on pure and carbon-doped α-iron in thermal equilibrium

A quantitative model for the evolution from random orientation to a unique texture in PVD thin film growth

Oxidational wear of TiN coatings on tool steel and nitrided tool steel in unlubricated fretting

Adhesion of diamond coatings on cemented carbides

Origin of characteristic subgap optical absorption in CVD diamond films