First principles study on small ZrAln and HfAln clusters: structural, stability, electronic states and CO2 adsorption

TL;DR

This study uses density functional theory to analyze the structural stability and electronic properties of small ZrAln and HfAln clusters, revealing specific stable geometries, electronic behaviors, and thermodynamic tendencies.

Contribution

It provides new insights into the stability, electronic structure, and charge transfer characteristics of Zr and Hf doped aluminum clusters, which were not previously detailed.

Findings

ZrAl4 and HfAl4 have lowest energy square pyramid structures.

HfAl6 shows the highest exothermicity among studied clusters.

HfAl6 tends to accept or donate electrons more readily.

Abstract

We report a first principles study based on density functional theory on the structural and electronic properties of transition metal Zr and Hf doped small aluminum clusters with 1 to 7 aluminum atoms. We have used B3PW91 with LANL2DZ basis set in Gaussian 09 package. The stability analysis reveals that the ZrAl4 and HfAl4 structures with C2v symmetry and square pyramid geometry are lowest energy structures. The most stable structures in ZrAl5 and HfAl5 are distorted tetrahedron type structure with symmetry C1. The binding energies per atom for transition metal doped Aln clusters increases with the cluster size, while the second order difference in total energy show oscillatory behavior with even and odd cluster size. The HOMO and LUMO gap for ZrAln is larger than the HfAln clusters except for n being 1 and 3. The HfAl6 has more tendency to accept or give away electrons. The negative charge exists on Zr and Hf indicating that the electron transfers from Al atom to transition metal, Zr and Hf. The thermodynamical analysis suggest that the HfAl6 cluster has highest exothermicity compared to not only all considered Al clusters but also other transition metal doped Al clusters reported in J. Phys. Chem. C, 120, 10027, 2016.