Probing the Magic Numbers of Aluminum–Magnesium Cluster Anions and Their Reactivity toward Oxygen

Abstract

We report a joint experimental and theoretical investigation into the geometry, stability, and reactivity with oxygen of alloy metal clusters Al(n)Mg(m)(-) (4 ≤ n+m ≤ 15; 0 ≤ m ≤ 3). Considering that Al and Mg possess three and two valence electrons, respectively, clusters with all possible valence electron counts from 11 to 46 are studied to probe the magic numbers predicted by the spherical jellium model, and to determine whether enhanced stability and reduced reactivity may be found for some Al(n)Mg(m)(-) at non-magic numbers. Al5Mg2(-) and Al11Mg3(-) exhibit enhanced stability corresponding to the expected magic numbers of 20 and 40 electrons, respectively; while Al7Mg3(-), Al11Mg(-), and Al11Mg2(-) turn out to be unexpectedly stable at electron counts of 28, 36, and 38, respectively. The enhanced stability at non-magic numbers is explained through a crystal-field-like splitting of degenerate shells by the geometrical distortions of the clusters. Al(n)Mg(m)(-) clusters appear to display higher oxidation than pure Al(n)(-) clusters, suggesting that the addition of Mg atoms enhances the combustion of pure aluminum clusters.

Communication: A density functional investigation of structure-property evolution in the tetrakis hexahedral C4Al14 nanocluster

“…[8][9][10][11] In our previous studies on core-shell C n Al 12 species, the n = 4 system has exhibited a unique behaviour. The original Al 12 shell generally preserved its near-icosahedral structure for n = 1 to 3, but, apparently due to an "oversized" carbon core, acquired a tetracapped-cube-like geometry for C 4 Al 12 . In light of its unique structure, completing the shell of Al atoms that surround the C 4 core, by capping the two remaining faces of the Al 8 cage, is a tempting prospect as this allows us to verify if such a highly symmetric system could be stable and to investigate its properties.…”

Chemical and Morphological Inhomogeneity of Aluminum Metal and Oxides from Soft X-ray Spectromicroscopy

“…If all the oxygen was associated with a layer of amorphous alumina (am-Al2O3, ρ = 2.3 g/cm 3 ), 38 then these values correspond to 88 ± 8 wt. % metallic aluminum and 12 ± 1 wt.…”

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

“…4 Aluminum is a light-weight and low-cost metal material, while Al clusters and doped-Al clusters have been widely investigated. 10 The mixed metal systems of magnesium and aluminum are lighter and cheaper than other Al based alloy, 11,12 having superiorities in the development of new materials for hydrogen storage. 13 Based on the density functional theory (DFT), small stable Mg Al clusters such as MgAl 4 14 16 From the famous magic cluster of Al 13 , previous theoretical studies were also focused on the structural and electronic properties of hydrogenated MgAl 12 clusters.…”

“…10 The mixed metal systems of magnesium and aluminum are lighter and cheaper than other Al based alloy, 11,12 having superiorities in the development of new materials for hydrogen storage. 13 Based on the density functional theory (DFT), small stable Mg Al clusters such as MgAl 4 14 16 From the famous magic cluster of Al 13 , previous theoretical studies were also focused on the structural and electronic properties of hydrogenated MgAl 12 clusters. [17][18][19][20] According to a spherical jellium 21 which the electronic configuration of clusters approaches a closed shell, magic clusters have the valence electron count of 2,8,18,20,34,40. .…”

“…Expected stabilities were found in Mg 2 Al 5 -, Mg 3 Al 11 -with 20 and 40 valence electrons. 12 However, Mg 3 Al 7 -, MgAl 11 -and Mg 2 Al 11 -non-magic clusters exhibit unexpected stabilities, 12 revealing that applications of the jellium model may be inapplicable in some cases of the Mg Al clusters.…”