Chemical Bonding in Gallides of the Rare-Earth Metals: from Zintl Concept to Positional-Space Approach

摘要

The composition and crystal structures of numerous compounds of the alkaline and alkaline-earth metals with tetrels can be understood within the framework of the Zintl concept1 applying the generalized Pearson rule2. E.g., the interpretation of the structural features of CaSi?, CaSi and Ca2Si by means of charge transfer from calcium to the silicon which leads to the formation of the polyanions with three-, two-bonded or isolated Si anions, can be found already in the handbooks3,4. The basis for such understanding is - among others - the sufficient number of valence electrons in the according system (cf., e.g., Ref. 5).