Random covalent model

The structure of a-C H films may be thus pictured as sp--carbon atoms in condensed aromatic clusters, dispersed in an sp- -rich matrix, which confers to the network its characteristic rigidity. This situation can also be regarded as a random covalent network in which the sp" clusters of a defined size take part in the structure as an individual composed atom with its corresponding coordination number [17]. Such kinds of models have been successfully used to describe the dependence of a-C H film mechanical properties on composition, hybridization, and sp" clustering [23]. 

One of the early models to describe the amorphous state was by Zachariasen (1932), who proposed the continuous random network model for covalent inorganic glasses. We are now able to distinguish three types of continuous random models ... 

A covalent model has been provided to explain the limiting range of carbon composition and the possible structure of the R3SnC t compounds (McColm et al. 1971). The perfect perovskite carbide structure would have a carbon atom in the octahedral site at the center of the unit cell. However, a random distribution of lanthanide and tin atoms occurs over all the fee sites. In this situation, a probability... 

Two models exist for prediction of the number of bonds between different elements. If a glass contains two elements, A and B, we might find bonds between two A atoms, between two B atoms, or between one A and one B atom. If the probability of each type of bond is given by the statistical probability based on the ratio of each type of atom in the composition, we term the structure a random covalent network, or RCN. On the other hand, if we assume that A-B bonds are always favored... 

Presented polymer mixtures are composed of amorphous macromolecules with different molecular architecture homopolymers and random copolymers, with different segments distributed statistically along the chain, form partly miscible isotopic and isomeric model binary blends. The mixing of incompatible polymers is enforced by two different polymers covalently bonded forming diblock copolymers. Here only homopolymers admixed by copolymers are considered. The diblock copolymer melts have been described recently in a separate review by Krausch [17]. 

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