Electronic structure and peculiar bonding properties of NdNiMg5 from first principles

• New NdNiMg5 shows drastic changes in electronic structure versus isostructural NdNi.
• Mg presence leads to enhanced cohesive energy, larger compressibility and brittleness.
• In NdNi bonding is ensured by Nd–Ni; in NdNiMg5, Nd–Ni, Nd–Mg, Ni–Mg and Mg–Mg participate in cohesion.
• Antiferromagnetic ground state confirmed from variational energies.

The newly found ternary compound NdNiMg5 has been studied within DFT based methodologies. Results of cohesive energy, charge transfers, elastic constants and electron localized function mapping as well as electronic structure and bonding properties have been compared with those of isostructural binary NdNi. The calculation results have shown that Mg substructures interlayering NdNi – like slabs exhibit different magnitudes of charge transfers all within range of metallic behavior and the different Mg substructures selectively bind with Nd and Ni substructures. As a consequence an enhanced cohesion with respect to binary intermetallic NdNi is identified. The whole set of elastic constants and their combinations in orthorhombic symmetry confirm the mechanical stability of NdNiMg5 with larger compressibility and less ductility (more brittleness) with respect substructures to NdNi. While in an intermetallic compound such as NdNi the bonding is ensured mainly by Nd–Ni interaction, in NdNiMg5 Nd–Ni, Nd–Mg, Ni–Mg as well as Mg–Mg participate to the bonding and the extra electrons brought by Mg are found within bonding states thus illustrating furthermore the enhanced cohesion of the ternary versus the binary systems.

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