PACS: 82.30.Cf; 82.30.Nr; 79.20.Nf
Springer Online Journal Archives 1860-2000
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
• )4, though it is expected to relax via formation of peroxidic bridges), and the oxygen-bridge vacancy (which in the absence of relaxation can be described as a diradical center (≡Si•)2– the E′′ center). These radicals react with the residual atmosphere according to completely new pathways: the bombardment in a CO2 atmosphere results in the formation of ester-like and carboxylate groups, stable up to 500 °C at least, inserted in the SiO2 network at the oxygen-bridge vacancies. The bombardment in a C2H4 atmosphere results in more complex configurations: the oxygen-bridge vacancy reacts at room temperature with ethylene forming a Lewis adduct which, after heating at 500 °C, presumably reverts to a -CH2-CH2- bridge in between silicon atoms; the silicon-link vacancy likely reacts with C2H4 forming CH3CHO. These conclusions, based on experimental data (mainly infrared spectroscopy), are also supported by extended quantum mechanical calculations (density-functional methods and ab initio molecular dynamics).
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