Regensburg 1998 – scientific programme

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DS: Dünne Schichten

DS 24: Postersitzung

DS 24.38: Poster

Thursday, March 26, 1998, 15:00–19:00, PF A

A Density Functional Tight Binding Study of Structure and Property Correlations in a-CH(:N) Systems. — •Th. K"ohler, Th. Frauenheim, P. Blaudeck, and K. H. Hoffmann — Institut für Physik, Technische Universität, Chemnitz, D-09127 Deutschland

The density functional (DF) method is used to investigate the correlations between structural, electronic and vibrational properties of a-CH(:N) systems of increasing nitrogen content. For structure model generation we apply an ensemble based adaptive schedule for parallel simulated annealing , where the total energy and forces are calculated by a non-orthogonal (DF-LDA) tight-binding approach. The high transferability of this scheme has previously been demonstrated by an accurate description of systems of all sizes, ranging from molecules, clusters to crystalline phases[1]. Based on recently performed studies of a-C and a-C:H structures, we discuss the correlations between the local bonding environment and the electronic/vibrational behaviour for various concentrations of nitrogen. Moreover, we analyse the nature of topological defects and prove that they lead to localizated electronic states and vibrations.

[1] D. Porezag, Th. Frauenheim, Th. Köhler, G. Seifert and R. Kaschner , Phys. Rev. B, 51, 12947-12957, (1995).