REACH requirements Terms Links

Note that, in all these calculations, very few terms containing more than a single rtJ factor were used. Inclusion of such terms improves the convergence of the basis, but these terms also introduce difficulties in the evaluation of the matrix elements. If the basis is constrained so that no more than a single rtJ factor appears in any term, these difficulties are minimized. This also dramatically reduces the number of terms required to reach a particular metric order. In more complex systems, such a basis produces integrals linking no more than four electrons, so that, despite its limitations, this basis can be very useful in calculations beyond lithium. 

Chain units that are involved in forming intermolecular cross-links require special attention as far as crystallization is concerned. When a sufficient number of intermolecular cross-links are imposed on a collection of linear polymer chains, a three-dimensional network structure reaching macroscopic dimensions is developed. Such structures are termed infinite networks. According to theory (1,2) the initial formation of a network occurs when the fraction of cross-linked units p exceeds a critical value pc that is expressed as... 

---