Quantenchemische Untersuchungen von Nitriden, Pernitriden und Oxidnitriden der Erdalkali- und Übergangsmetalle

摘要

In this work nitrides, pernitrides and oxypernitrides of the alkaline earth and transition metals are investigated using quantum chemical methods. In the first part, the existence of two different N2-species is confirmed by characterizing (such as bond length, raman frequencies and COHP analysis) the experimentally well-known compounds BaN2 and PtN2. After resolving the basic question of the composition of the pernitride unit itself, several MN2 compounds were investigated in terms of stability, properties and synthesis conditions. The iron-nitrogen phase diagram at high pressures and temperatures was examined in the second part of this work. Experimentally found phase transitions were distinguished between pressure and temperature induced phase transition by means of quantum chemical calculations. In addition, some phase transitions were predicted. The third part is about the compound FeON. In order to find the thermodynamical minimum, cells with different characteristics were constructed. These characteristics led to iron oxidation states between +2 and +5. The structure lying lowest in energy should be accessible through a high-pressure synthesis and would be the first compound of the new class of oxypernitrides.