Why is BeGeN2 different? A computational bonding analysis

Abstract

Until recently, all known ordered II–IV-N₂ materials crystallised in the β-NaFeO₂-type in space group Pna2₁. BeGeN₂, however, crystallises in space group Pmc2₁, with a different cation ordering motif long anticipated for this materials class. Chemical bonding analysis is used to rationalise this particular behaviour. Using crystal orbital Hamilton populations and crystal orbital bonding indices as indicators for the nature and strength of the chemical bonding, the difference in ionicity between Be–N and Ge–N bonds is identified as the main driving force allowing this particular structural motif.