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A DFT-Study of Structure and Properties of Amorphous SiCN

Published online by Cambridge University Press:  01 February 2011

Peter Kroll*
Affiliation:
Department of Inorganic Chemistry, RWTH Aachen, Prof.-Pirlet-Str. 1, 52056 Aachen, Germany
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Abstract

Structures and properties of amorphous silicon carbonitride (a-SiCN) materials are studied using density functional methods. Topologicaly different models of a-SiCN with 112-156 atoms each were generated from continuous alternating random networks. The networks have distinct topologies which result in a different chemical bonding in the investigated structural models. A first model consists of Si-N and Si-C bonds only. For such materials with “anionic” carbon we found the highest bulk modulus. However, the network strain is largely due to the high SiC content, resulting in bond ruputre and redistribution in the amorphous structure. A second model consists of Si-N and C-N bonds only. We found that a tetrahedral coordination of “cationic” carbon in such a compound is unstable at elevated temperatures, as indicated by Car-Parrinello molecular dynamic (CPMD) simulations. A third model consists of amorphous Si3N4 as host structure and a segregation of graphitic C inside a pore. Such a model, although low in density, has an enlarged bulk modulus, comparable to the “anionic” model.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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