The geometric and electronic structures of AlnNam (n=5, 6; n+m≤10) clusters

3 years ago

The geometric and electronic structures of AlnNam (n=5, 6; n+m≤10) clusters

The low-energy structures of Al5Nam (m=1–5) and Al6Nam (m=0–4) are searched by using the genetic algorithm combined with MOPAC package. The stabilities and the electronic structures are studied by density functional theory models and by first principle perturbation theory at MP4 level. The results show that the Na atoms are located at the outside of the clusters. Analysis on the density of states and the charge distribution indicate the sodium atoms transfer their 3s electrons to aluminum and exist as +1 cations. The molecular orbitals agree with the types predicted by the jellium model, and Al5Na5 and Al6Na2 show enhanced stabilities as the 20 valence electrons form closed electronic shells. However, the valence orbitals don’t encompass the Na⁺ cores. The electron localization function clearly demonstrates that the valence electrons reside at the outside of the Al³⁺ cores, and the Na⁺ cores are exposed at the outside of the valence electrons. All the results confirm that Aln moieties in the AlNa binary clusters form Zintl anions and the Na⁺ cations are ionically bonded to them. It suggests AlNa clusters can be used as building blocks to form cluster-assembled Zintl-phase materials.

Publisher URL: www.sciencedirect.com/science

DOI: S2210271X17303274