A High Pressure Study on NH4Pb2Br5 Type Compounds Part II: Electronic Structure and Changes under High Pressure

Abstract

AbstractIn this work, we present a theoretical study (based on DFT‐calculations) of the electronic properties of compounds crystallising in a NH4Pb2Br5 type structure in a wide pressure range. The main focus of this study is to elucidate the nature of bonding of the ns2‐cations at ambient and elevated pressure.For a better understanding of the structure and bonding, the DOS of these compounds are evaluated and discussed on the basis of a simple model assuming mainly ionic interactions. The calculations are complemented by an orbital analysis using the crystal orbital Hamilton population (COHP) and an analysis of the electronic density topology with the electron localisation function (ELF). Structural and theoretical investigations give results that are in excellent agreement: The DFT‐calculations confirm the existence of bonding interactions between the ns2‐cations at elevated pressure.Our study indicates that the “character” of the additional electron pair changes with increasing pressure from nonbonding to bonding in agreement with a simple model system of two interacting ns2‐cations.