Application to the Structural Study of Disordered Phases

It is of special interest for many applications to consider adsorption of fiuids in matrices in the framework of models which include electrostatic forces. These systems are relevant, for example, to colloidal chemistry. On the other hand, electrodes made of specially treated carbon particles and impregnated by electrolyte solutions are very promising devices for practical applications. Only a few attempts have been undertaken to solve models with electrostatic forces, those have been restricted, moreover, to ionic fiuids with Coulomb interactions. We would hke to mention in advance that it is clear, at present, how to obtain the structural properties of ionic fiuids adsorbed in disordered charged matrices. Other systems with higher-order multipole interactions have not been studied so far. Thermodynamics of these systems, and, in particular, peculiarities of phase transitions, is the issue which is practically unsolved, in spite of its great importance. This part of our chapter is based on recent works from our laboratory [37,38]. 

The oxide Ba2In205 is another well-studied phase that adopts the brownmillerite structure. This material disorders above 930°C to a perovskite-type structure containing oxygen vacancies. Both the Sr-Fe and Ba-In oxides are of interest for electrochemical applications in fuel cells and similar devices (Section 6.10). 

The solid-state NMR technique can be used to deduce quantitative measurements of phase composition, as has been reported for the anhydrate and dihydrate phases of carbamazepine. The applications of solid-state C-NMR spectra for the study of polymorphs and solvates can go beyond evaluations of resonance band positions, making use of additional spectral characteristics. For instance, studies of Tip relaxation times of furosemide polymorphs were used to show the presence of more molecular mobility and disorder in Form II, while the structure of Form I was judged to be more rigid and uniformly ordered. " ... 

In the last six years, TBMD has been applied to the study of structural, dynamical, and electronic properties of various covalent systems, including crystalline structures, disordered liquid and amorphous phases, clusters, surfaces, defects, and even more complex hydrogenated systems. In this section we highlight some of these applications. We focus primarily on the results of our work work from other groups will be covered only briefly. 

---