Chemical Bonding Analysis for Complex Solids in Real Space

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The analysis of chemical bonding performed in real space as an alternative to the traditional orbital-based methods is an actively developing field of research, gaining more and more popularity in the whole chemical community. The main advantages of these methods are universality (can be equally well applied to the results of any calculation method), simplicity of applications (analysis is not directly based on a large set of one-electron states delocalized over the whole system) and firm theoretical background (corresponding formalism is usually based on reduced density matrices). These methods are especially beneficial for solids, where one usually has lots of delocalized one-electron states and non-atom-centered basis sets like the planewaves, which are difficult to cleanly decompose into atomic contributions. Probably the most prominent are the quantum theory of atoms in molecules (QTAIM) and the electron localization function (ELF) but other powerful tools also exist: among them are electron localizability indicators (ELI, making it possible to connect both real-space and orbital pictures), delocalization indices (DI, expressing the degree of electron localization in space region), domain-averaged Fermi hole orbitals (DAFHO, allowing to recover many orbital-based bonding concepts) and many more. Modern experimental methods of inorganic synthesis open new possibilities on discovering novel solids with complex structures formed itself by complex building blocks such as condensed mixed metal clusters. These confined metals are spatially often organized like natural heterostructures, but on the smaller scale and possess extraordinary physical properties. Tentative analysis of the highly nontrivial bonding patterns within these compounds is challenging. Traditional orbital-based methods like bandstructure analysis can also hardly be applied because of the large number of one-electron states especially in case of compounds containing transition metals. Chemical bonding analysis using real-space indicators should be a suitable tool for such complex systems providing compact and visual local representation of bonding pictures independently on the complexity of the system studied. It is the objective of the project to develop an universal and efficient approach to the real-space bonding analysis of complex solids and to use them to understand the chemical bonding in the confined metals class of compounds. It should allow one to derive the principles of construction, that may help to tailor the development of new compounds with desired structural organization. In the same time, this may also allow to reveal direct "crystal structure - electronic structure - physical properties" interrelations and thus open the way to the design of novel materials.