The bond ionicity in ANB8−N compounds from maximally localized Wannier functions

• The newly developed ionicity scale of Abu-Farsakh and Qteish have been thoroughly assessed, by investigating the ionicity in an extensive list of ANB8−N compounds.
• The ionicity trends in these compounds is discussed, in comparison with those of the most accepted and widely used ionicity measures.
• The ionicity in the alkaline-earth oxides, which is a controversial issue, is found to increase by going from MgO to BaO.
• The volume dependence of the ionicity is also thoroughly investigated.

The bond ionicity in seventy two ANB8−N compounds is investigated according to the recently introduced first-principles ionicity scale, based on the centers of the maximally localized Wannier functions, which has several interesting features. The obtained bond ionicities (qi) are found to exhibit the expected trends, according to electronegativity arguments. In particular, the bond ionicity in the alkaline-earth oxides increases by going from MgO to BaO. A strong crystal structure dependence of qi is observed. A critical value of qi (of 0.91) that separates between the tetrahedrally and octahedrally coordinated systems is inferred directly from the calculated values of qi. The volume dependence of qi is investigated for all the considered compounds and found to reduce by volume decrease for most of the studied systems. The adopted ionicity scale is established as a very strong competitor to the most widely accepted Phillips and Pauling ionicity measures.