Shell macro-molecules

ABSTRACT. A Lennard-Jones potential is used to derive for-mulaefor the potential of interaction between shell macro-molecules and gas atoms. Calculations are carried as far as thespherlcal symmetry approximation. The potential of interaction determines the stability of a shell topological compound. When the distance R between a shell molecule and a gas atom is equal the radius 1 of the outer shell, the potential is the highest and determines a barrier, which must be lower than an energy of the trapped / by the shell molecule / atom to be released. 

The most straightforward way of using quantum-chemical information at the atomistic level is by means of a force field. This requires that no truly electronic processes (chemical reactions, electronically excited states) are involved and that basically a description of a (macro)molecule in its closed-shell ground state is desired. 

As mentioned earlier, biological systems have developed optimized strategies to design materials with elaborate nanostructures [6]. A straightforward approach to obtaining nanoparticles with controlled size and organization should therefore rely on so-called biomimetic syntheses where one aims to reproduce in vitro the natural processes of biomineralization. In this context, a first possibility is to extract and analyze the biological (macro)-molecules that are involved in these processes and to use them as templates for the formation of the same materials. Such an approach has been widely developed for calcium carbonate biomimetic synthesis [13]. In the case of oxide nanomaterials, the most studied system so far is the silica shell formed by diatoms [14]. 

Biomineralization. In biomineralization, inorganic elements are extracted from the environment and selectively precipitated by organisms. Usually, templates consisting of suitable macro-molecules serve as a substrate for the heterogeneous nu-cleation of bulk mineralized structures such as bone, teeth and shells. Biological control mechanisms are reflected not only in the type of the mineral phase formed but also in its morphology and crystallographic orientation (Mann et al., 1989 Lowenstamm and Weiner, 1989). Two examples (perhaps oversimplified) may illustrate the principle (Ochial, 1991) ... 

The covalent bond was already discussed in section 1.1. Atoms that lack only a few electrons to achieve a fully occupied outer shell share some of their electrons. As an example, the H2 molecule was explained. To form a solid with strong bonds between the atoms, it is insufficient if each electron lacks only one electron because in this case a two-atomic molecule will form only. An atom with a valency of four, like carbon, can form large units in which each atom has four bonded neighbours. Figure 1.13 shows the resulting carbon macro-molecule, diamond. Other elements with four valencies, like silicon and germanium, form similar structures. 

Site binding of a counterion to a polyelectrolyte involves the replacement of a given number of the p water molecules of the first hydration shell by ligands from the macro-... 

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