Metals, determination atom trapping

In ceramics, unlike many industries, AAS has not been greatly used, partly because of chemical and other matrix problems, and partly because XRF appeared on the scene shortly after AAS came into use. Its main application in the ceramic industry has been in the determination of metal release from ceramic ware. This is a class of tests designed to establish the likelihood of lead or cadmium leaching from ceramic ware and involves a 24 h extraction at 22°C with 4% (v/v) acetic acid and subsequent determination of lead and cadmium by flame AAS. Current legislation in the USA is driving limits to a level where atom trap AAS, ICP, or graphite furnace AAS is needed. 

Before a detailed presentation of the ab initio dynamics simulations, first the fundamental difference between atomic and molecular adsorption on the one hand and dissociative adsorption on the other hand has to be addressed. Then I will briefly discuss the question whether quantum or classical methods are appropriate for the simulation of the adsorption dynamics. This section will be followed by a short introduction into the determination of potential energy surfaces from first principles and their continuous representation by some analytical or numerical interpolation schemes. Then the dissociative adsorption and associative desorption of hydrogen at metal and semiconductor surfaces and the molecular trapping of oxygen on platinum will be discussed in some detail. 

Lundstrdm, 1981 Lundstrom and Soderberg, 1981 Lundstrdm et al., 1975 Shivaraman et al., 1976), (2) absorbed H reaction with Pd to form a hydride with lower work function (Steele et al., 1976), and (3) formation of a Pd-H system without chemical bonding of H atoms, with a lower work function (Lewis, 1967). The second one concerns the penetration of H atoms through the oxide layer and the formation at the SiO /Si interface of trapping states that determine tunneling of electrons between the metal and the semiconductor (Keramati and Zemel, 1982 Zemel et al., 1980 Kera-mati, 1980). 

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