First Principles Study of Topochemical Effects and Electronic Structure Relationships between ANCl and A2N2Se (A = Zr, Ce) Assimilated to Pseudo-Binaries: {AN}Cl and {A2N2}Se

Abstract

Topochemical and electronic structure relationships are shown upon going from ANCl to A 2 N 2 Se (A = Zr, Ce) through metathesis. The chalcogen Se (divalent) displacing halogen Cl (monovalent) modifies the arrangements of AN monolayers within ANCl (.. . Cl|{AN}|Cl. .. sequences) to double layers in A 2 N 2 Se (.. . Se|{A 2 N 2 }|Se. .. sequences). The investigation carried out in the framework of the quantum density functional theory DFT points to peculiar features pertaining to the dominant effect of the AN covalent bond stronger than ionic A-Cl and ionocovalent A-Se, as identified from analyses of bonding from overlap integral, charge transfer, electron localization function mapping. Electronic density of states shows semi-conducting behavior due to the tetravalent character of A. The resulting overall pseudo-binary compounds are expressed formally with full ionization as {AN}Cl and {A 2 N 2 }Se.