Structural stabilities and electronic properties of Mg28-nAln clusters: A first-principles study

Abstract

In this paper, we have constructed the alloy configurations of Mg28-nAln by replacing atoms at various possible positions, starting from the stable structures of Mg28 and Al28 clusters. According to the symmetry of the cluster structure, the isomers of these initial structures have been screened with the congruence check, which would reduce computational hours and improve efficiency. Using the first-principles method, the structural evolution, mixing behavior and electronic properties of Mg28-nAln clusters are investigated for all compositions. We conclude that Al atoms prefer to reside in the central positions of Mg−Al clusters and Mg atoms tend to occupy the peripheral location. The negative mixing enthalpies imply the stabilities of these Mg-Al clusters and thus possible applications in catalysis and hydrogen storage materials. Among Mg28-nAln clusters, Mg24Al4, Mg21Al7, Mg14Al14, Mg26Al2 and Mg27Al1 present relatively high thermodynamic stabilities, and the electronic properties of these stable structures are discussed with the charge distributions around the Fermi level.

Au-Ru nanoparticles in catalysis, analysis from first-principles calculations

“…A negative value indicates a favorable mixing tendency and a greater stability. It can be defined as follows (Lu et al, 2017):…”

Cluster structure prediction via CALYPSO method*

“…We have adopted CALYPSO method to investigate the Mg-Al binary alloy clusters, [90] as shown in 20 valence electrons and large energy gap, is identified to be magic cluster. [90] Moreover, another similar work, [91] focused on Mg 28−n Al n cluster, has reported five different stoichiometries of Mg-Al clusters, which present outstanding thermodynamic stabilities. As for RuGe n cluster, we have reported a systematic study of the relative stability and electronic properties of Ru-doped Ge clusters in the size range of 3 ≤ n ≤ 12.…”

Density Functional Theory Modeling of Reactions of Addition of H2 Molecules to Magnesium Clusters Mg17M Doped with Atoms M of Transition 3d Elements

“…While Al atoms prefer to occupy the inner (endohedral) sites, the Mg atoms form the surfaces of the clusters. The neutral mixed Mg 24 Al 4 , Mg 21 Al 7 , Mg 14 Al 14 , Mg 26 Al 2 , and Mg 27 Al 1 and “magic” mononuclear Mg 10 and Mg 17 clusters were predicted to be the most stable species (see refs and for details).…”

“…To date, hydrides of the Mg m H n series ( m = 1–4 and n = 1–8), mixed magnesium–aluminum clusters Al n Mg m ( m ≤ 3, n + m ≤ 15), and their negative ions have been detected experimentally. − Their DFT calculations demonstrated that the most stable species are the “magic” clusters Al 5 Mg 2 – , Al 11 Mg 2 – , Al 7 Mg 3 – , and Al 11 Mg 3 – . Systematic DFT studies performed for a wider family of mixed Mg 28– n Al n clusters ( n = 0–28), Mg 55‑ n Al n ( n = 0–55), and homonuclear Mg n isomers ( n = 2–56) − ,, have demonstrated that the enthalpies of Mg/Al mixing are negative for all components. While Al atoms prefer to occupy the inner (endohedral) sites, the Mg atoms form the surfaces of the clusters.…”

“…11−13 Their DFT calculations demonstrated that the most stable species are the "magic" clusters Al 5 Mg 2 − , Al 11 Mg 2 − , Al 7 Mg 3 − , and Al 11 Mg 3 − . Systematic DFT studies performed for a wider family of mixed Mg 28−n Al n clusters (n = 0−28), 14 Mg 55-n Al n (n = 0−55), 15 and homonuclear Mg n isomers (n = 2−56) [16][17][18]20,21 have demonstrated that the enthalpies of Mg/Al mixing are negative for all components. Of special interest are the quantum-chemical studies of mechanisms of elementary hydrogenation reactions.…”