Intermetallic compounds are formed by elements located left from the Zintl line in the Periodic Table. For interpretation of their chemical and physical properties a better understanding of the chemical composition and bonding in crystal structures of these substances is necessary. Especially the chemical bonding in intermetallic compounds is a rather open question . An application of new quantum-chemical tools in real space like the electron localizability approach [2-5] opens the way to real-space definition of the basic categories for chemical bonding description like covalence or ionicity  or polarity . On that base, the Pauling‘s 8–N rule is re-defined for the real space and used for a consistent and quantitative treatment of heteropolar bonding situations exemplarily for compounds of the MgAgAs type and their relatives . The QTAIM Madelung energy calculated using effective charges and the exchange energy obtained by point-charge approximation from the delocalization indexes were used to identify favourable element combinations for new MgAgAs-type compounds. Two so-predicted high-temperature phases VIrGe and the low-temperature modification of HfPtGe showing this type of crystal structure were prepared and characterized . Furthermore, the electron localizability approach allows to study even the weak van-der-Waals bonding  and visualize the multi-centre interactions .
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