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The potential energy surface for the Ar/Ag(111) system is studied within the local density approximation. Results for N atom clusters, where N=4, 10, and 19, are compared with the potentials obtained with slabs with summation of pair potentials. This last method predicts the threefold hollow site as equilibrium site. However, the larger clusters find the top site as adsorption site. On the top site, the adsorption height and energy are calculated as 3.2 Å and 0.10 eV, respectively. The physisorption energy is in reasonable agreement with experimental data, in spite of the LDA level of theory used. Thus the Ag(111)–Ar system is a new example where LDA appears to describe a van der Waals system with reasonable accuracy. A correction to the sum of pair potentials is given that effectively reproduces the calculated potentials at threefold hollow site and top site. [ABSTRACT FROM AUTHOR]

The influence of relativity on the binding in the Pt–O molecule is investigated using density functional calculations and proves to be quite important, not only for the potential well but also for the repulsive wall. Using a Born–Mayer fit to this interatomic gas phase potential, we perform a classical trajectory study on high energy O2/Pt(111) scattering (Ei=80 eV). The Born–Mayer form of the interatomic potential leads to a higher degree of dissociation for O2/Pt(111) than for O2/Ag(111) which is also experimentally found. The role of relativity turns out to be significant. The dissociation mechanism, however, does not change when going from O2/Ag(111) to O2/Pt(111). The molecules were found to first gain primarily rotational energy, which is largely transfered to vibration at the turning point of the second atom, in the case of finally dissociating molecules. Since the calculated dissociation in the case of platinum is still less than found experimentally, we investigate the influence of better fits to the interatomic potential, as well as inclusion of the potential well. It is possible to improve agreement with the experimental results by directly reducing the long range of the Born–Mayer potential. [ABSTRACT FROM AUTHOR]

In the automotive industry, color quality control is increasingly done by reflection measurements. We discuss how color tolerances are set in specifications to suppliers of add-on parts and to paint suppliers. We mention several factors that often lead to unrealistically tight settings, and therefore to incorrect rejections and unnecessary high productions costs. We show that this is likely to occur when the dEab color difference equation is used, or when a strict criterion separating pass from fail is used instead of specifying a 'grey area' where instrumental monitoring needs to be followed by visual assessments. Unrealistically, tight tolerances also result from halving tolerances in the supply-customer chain in an attempt to compensate color variations due to uncontrolled application conditions. Tolerances should be widened further when a gap separates an add-on part from the car body, making visual discrimination of color differences less critical. Other common situations where tolerances should be widened are the presence of visual texture in effect coatings, the lightness of metallic coatings becoming very high (L*> 100) and measurement geometries close to the gloss angle. Finally, we address the issue that instrumental color tolerances should not be tighter than what is allowed by instrumental reproducibility, repeatability, and inter-instrument agreement. Accounting for these factors, we provide a set of reasonable values for tolerances on color and on visual texture parameters, based on our own practical experience. But realistic tolerance values depend very much on actual conditions, and should be agreed in tripartite discussions among automotive industry, suppliers of add-on parts, and paint supplier. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 88-98, 2014 [ABSTRACT FROM AUTHOR]

We have investigated how texture and color combine when assessing the appearance of special effect coatings. In a previous study, the most important aspects of the texture of special effect coatings were identified as diffuse coarseness and glint impression. In the present study, objective measurements of these parameters are carried out using a recently developed instrument, and these data are combined with spectrophotometer data under six geometries. The instrumental data and visual data are analyzed using statistical techniques. From these visual data we were able to create a total appearance score which strongly correlates with the measurements of color and texture differences using this instrument. In this way a calculation procedure has been developed yielding predictions on acceptability that correlate well with visual judgments. Also, the added value of reflection data close to the gloss angle is demonstrated. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2011 [ABSTRACT FROM AUTHOR]