A Review on Binary Alkaline‐Earth Trielides: an Overview of Compositions and Structures, of their Stabilities and Energetics and of Criteria for the Validity of the Zintl‐Concept

Abstract

Omitting alloys with a compositional range we present a compilation of binary alkaline earth trielides AExTRy together with results of DFT calculations to estimate total energies and energies of formation in comparison and to analyse the distribution of charges at the atomic positions in a Bader analysis of the electron density. In a comparison of many structures, we furthermore analyse the effect of bonding on this charge distribution and reflect on the real bonding patterns in comparison with our expectations according to the Zintl concept, and we find mechanisms blocking an electron transfer as favoured by the electronegativity differences. We have subjected a variety of structural parameters together with the DFT results to a Principal Component Analysis to explore their relationship which we describe in the form of correlation matrices and biplots. The Zintl rules turn out to be a very slack guideline in rationalizing the structures of these compounds.