Topological Structure of Defects

As already mentioned, the layered structure of cholesteric materials imposes certain limitations on the topological classification of defects based on ho-motopy groups a more general theory is still lacking. In this section we discuss macroscopic defects such as focal conic domains and oily streaks whose existence depends crucially on the layered character of ordering. 

In general, differences in chemical bonding and electron configuration between carbon atoms and dopants mandate the deviation from the geometric and electronic equilibrium structure of the aromatic layers in CNTs. As a consequence, topological defects such as Stone-Wales defects are formed with increased probability [37]. 

Fracture processes become very different in the glassy state as compared with the rubbery state. In the glassy state, the sensitivity of fracture to network topology is lost. The chemical structure of the network, crosslink density and the type of bond overloading do not play a key role and defects of glassy samples become very important. 

Presently, the simulation of real metal surfaces with defects of all sorts is hampered by the restriction of system size and also because only little quantitative information is available concerning the specific electronic structure near these defects and its consequences for the binding of water molecules and ions. However, first steps into this direction were made recently Siepmann and Sprik [51], who investigated the influence of surface topology on water/electrode systems, and by Nagy and Denuault [98, 99], who extended the platinum-water potential to defect surfaces. However, since they did not take into account the electronic structure of the metal, their approach is purely geometrical. 

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