Electronic structure and chemical bonding in LaIrSi-type intermetallics

The cubic LaIrSi type has 23 representatives in aluminides, gallides, silicides, germanides, phosphides, and arsenides, all with a valence electron count of 16 or 17. The striking structural motif is a three-dimensional network of the transition metal (T) and p element (X) atoms with TX_3/3 respectively XT_3/3 coordination. Alkaline earth or rare earth atoms fill cavities within the polyanionic [TX]^δ- networks. The present work presents a detailed theoretical study of chemical bonding in LaIrSi-type representatives, exemplarily for CaPtSi, BaIrP, BaAuGa, LaIrSi, CeRhSi, and CeIrSi. DFT-GGA-based electronic structure calculations show weakly metallic compounds with itinerant small magnitude DOSs at E_F except for CeRhSi whose large Ce DOS at E_F leads to a finite magnetization on Ce (0.73 μ_B) and induced small moments of opposite sign on Rh and Si in a ferromagnetic ground state. The chemical bonding analyses show dominant bonding within the [TX]^δ- polyanionic networks. Charge transfer magnitudes were found in accordance with the course of the electronegativites of the chemical constituents.