Search

The geometries, stabilities and electronic structures of AlnCum (n = 5–9, m = 1–3) clusters were explored by using the genetic algorithm combined with ab initio methods. The geometric structures are almost spherical when the valence electrons are around the magic number 20, otherwise the structures are oblate or prolate. The stabilities of the clusters are related to both the Cu/Al ratios and the electronic configurations. The clusters with lower Cu/Al ratios have high stabilities. The molecular orbitals are in accord with the shell structures predicted by the jellium model. The 3d orbitals of the Cu atoms are localised, although their orbital energies are between the 1P and 1D jellium orbitals. The Al6Cu2 with 20 valence electrons forms closed 1S21P61D102S2 shells, and shows large binding energy and removal energy, large ionisation potential and small electron affinity. For the no-magic clusters, the structure deformation leads to crystal-field-like splitting of the degenerate shells and stabilises the clusters. [ABSTRACT FROM AUTHOR]

By using genetic algorithm combined with B3LYP and QCISD methods, this paper investigates the stabilities and electronic structures of Al6OMm (M = Na, K; m = 2,4,6) and a few other AlnXNam (X = C, N, O) clusters. The results show that the nonmetal doped metal clusters with 26 valence electrons have enhanced stabilities and large energy gaps. This paper extends the Jellium model for the application to the nonmetal doped metal clusters and explains the electronic origin of this strong magic structure. The nonmetal X atom is situated in the centre of the magic clusters. The 2s/2p orbitals of the central atom interact strongly with the superatomic 1S/1P orbitals and form bonding and antibonding orbitals. The bonding orbitals make the C/N/O atoms form s2p6 shell closure, and the antibonding orbitals make the metal moieties form closed 2S22P6 shells. The 26 valence electrons form closed s2p6S2P6D10 shells, and this electronic configuration can be taken as the combination of the octet rule and 18-electron rule. The octahedral Al6O2− core is a superatomic anion with great stability, and it can be used as building blocks to assemble Zintl phase materials by interaction with alkali metals. [ABSTRACT FROM AUTHOR]

The spherical jellium model predicts that metal clusters having 18 and 20 valence electrons correspond to the magic numbers and will show specific stabilities. We explore in detail the geometric structures, stabilities and electronic structures of Al-Mg clusters containing 18 and 20 valence electrons by using genetic algorithm combined with density functional theories. The stabilities of the clusters are governed by the electronic configurations and Mg/Al ratios. The clusters with lower Mg/Al ratios are more stable. The molecular orbitals accord with the shell structures predicted by the jellium model but the 2S level interweaves with the 1D levels and the 2S and 1D orbitals form a subgroup. The clusters having 20 valence electrons form closed 1S1P1D2S shells and show enhanced stability. The Al-Mg clusters with a valence electron count of 18 do not form closed shells because one 1D orbital is unoccupied. The ionization potential and electron affinity are closely related to the electronic configurations; their values are determined by the subgroups the HOMO or LUMO belong to. Graphical abstract: [ABSTRACT FROM AUTHOR]

• The C-doping enhances the stabilities of aluminum-alkali metal clusters. • Al 6 CM 4 (M = Li, Na, K) are magic clusters and Al 6 C4− forms a superatomic anion. • Al 6 CLi 4 is most stable as the alkali atoms are ionically bond to the central anion. • We extend the Jellium model to nonmetal doped metal clusters. The stabilities and electronic structures of Al 6 CM n (M = Li, Na, K; n = 2, 4, 6) are studied by evolutionary algorithm combined with ab initio methods. The strong attraction of the C4+ core to the valence electrons makes the 2S state considerably lower and the degenerated 2P6 being located in-between the split 1D10 states, so the 26 valence electrons form closed 1S21P62S21D102P6 shells. C-doping enhances considerably the stabilities of metal clusters. In Al 6 CM n clusters, the Al 6 Cq− with nearly all the valence electrons form Zintl anions and the M+ cations are ionically bonded on the peripheries. As Li+ has smallest radius, Al 6 CLi 4 possesses strongest thermal and chemical stabilities. The electronic structure of Al 6 C4− accords with the 8 + 18-electron rule and the Wade-Mingos rule, and can be regarded as a superatomic anion with specific stability. It can be used as building blocks to form Zintl phase structures by combining with metal counterparts. [ABSTRACT FROM AUTHOR]

This article investigated the low‐energy structures of Al6NamC (m = 2, 4, 6, 8) clusters and their electronic structures by using genetic algorithm combined with density functional theory and configuration interaction methods. The computations show that the C atoms prefer sitting at the center, whereas the Na atoms tend to locate at the outside of the clusters. The valence molecular orbitals (MOs) agree well with the prediction of the jellium model. The stronger attraction of the central carbon to the valence electrons will depress the potential energies locally, which makes the 2S level go obviously lower and the 2P and 1D orbitals form a sub‐band. The 26 valence electrons in Al6Na4C form closed 1S21P62S21D102P6 shells and correspond to a new magic structure. The MOs and electron localization function show that the sodium cores are exposed at the outside of the valence electrons and form naked cations. The contraction of the valence electrons because of the carbon doping enhances the charges on the Al6C moieties, and the Na+ cores on the peripheries are ionically bonded to the Zintl anions (Al6C)q−. The Al6Na4C has a tetrahedral structure with symmetry Td, and it may be used as building blocks to synthesize Zintl solid. The carbon atom doped in Al‐Na clusters depresses the potential locally and causes the 2S/2P orbitals to be considerably lower than that in pure metal clusters. The 26 valence electrons of Al6CNa4 form closed 1S21P62S22P61D10 shells and correspond to a new magic number with enhanced stability and large energy gap. The Al6C forms a 4− anion and Al6CNa4 is a potential building block for cluster assembled materials. [ABSTRACT FROM AUTHOR]

Hydrogen in borohydrides M(BH 4) n form BH 4 − unit and the binding strength is dominated by the B–H bonds. The M−H interactions regulate the B–H bonds and the stabilities depend on the electron donor properties of metal atoms M. The crystal structures of Sn(BH 4) 4 are determined by using global optimization algorithm combined with density functional theories, and the stabilities, electronic properties and bonding natures are systematically compared with other borohydrides of Zr, Al, Mg, Na. Sn transfers 41% of its valence electrons while Na/Mg transfers 84%/82%. The Sn–H bond is of covalent nature with strong polarities, and the covalent Sn–H interaction weakens the B–H bonds. The covalent interactions of different bonds are evaluated using crystal orbital Hamilton populations (COHPs). The results show that both the ionic and covalent interactions of the B–H bonds are obviously weaker in Sn(BH 4) 4 than in other borohydrides. With hydrogen content of 9.0 wt%, Sn(BH 4) 4 may be a promising hydrogen storage material working at moderate temperatures. 1 Crystalline phases of Sn(BH 4) 4 are determined. 2 Polarized covalent Sn–H bond weakens B–H interactions in BH 4 − units. 3 Binding of hydrogen in Sn(BH 4) 4 is weaker than in borohydrides of Zr, Al, Mg, Na. 4 Hydrogen storage capacity in Sn(BH 4) 4 reaches 9.0 wt%. [ABSTRACT FROM AUTHOR]

• The deformation coefficients δ and ε of geometric structures are approximately equal to 1.0 at the 40 valence electrons count. The geometric structures of Al-Cu clusters are spherical when the numbers of the valence electrons around the magic number 40, otherwise the geometric structures of cluster are oblate or prolate. • The stabilities of Al-Cu clusters relate to the Cu/Al ratios and the electronic configurations. Doping Cu atoms in the Al n clusters weakens the stability of the clusters. However, the Al 13 Cu, Al 13 Cu 2 and Al 12 Cu 3 clusters with 40, 41 and 39 valence electrons possess higher stability. • In Al 13 Cu cluster, the 3d orbitals of the central Cu atom interact strongly with the superatomic 1D orbitals of the cluster and formed five bonding orbitals and five antibonding orbitals. • Including ten 3d electrons of Cu atom, "50 valence electrons" in Al 13 Cu cluster formed 1S21P63d101D102S21F142P6 closed shell and the molecular orbitals accord with the shell structures predicted by the Jellium model. The 3d electrons of Cu atom don't affect the Jellium model of the cluster. The properties of Al n Cu m (n = 10–15, m = 1–3) clusters are explored using genetic algorithm combined with density functional theory (GA-DFT). The geometric structures of Al-Cu binary clusters are spherical when the numbers of the valence electrons are around the magic number 40 predicted by Jellium model. The stabilities decrease as the number of doping Cu atom increases. The stabilities also relate to the electronic configurations. In Al 13 Cu-a cluster, the 3d orbitals of the central Cu atom interact strongly with the superatomic 1D orbitals and formed five bonding orbitals and five antibonding orbitals. The bonding orbitals are dominated by 3d orbitals of Cu, and antibonding orbitals are composed mainly of the superatomic 1D orbitals. The "50 valence electrons" (including 3d10 of Cu) form closed 1S21P63d101D102S21F142P6 shells, and this electronic configuration can be taken as the combination of 40-electron rule. The 3d electrons of Cu atom don't affect the Jellium model of the cluster. [ABSTRACT FROM AUTHOR]

The structures of Al 6 OK 2 and Al 7 N/CK are determined using unbiased genetic algorithm combined with ab initio methods. It was experimentally confirmed that Al 7 C− possesses exceptional stability. This study presets the interpretation for the hetero magic clusters. The delocalized Jellium orbitals of the metal moieties and the atomic orbitals of the nonmetal atom interact strongly and form bonding and antibonding orbitals. The orbital interactions lead to closed s2p6 shells of the nonmetal atom and the 18-electron S2P6D10 shells of the metal moieties. The 26 valence electrons correspond to a strong magic number. Al 6 OK 2 cluster is formed by ionically bonding two K+ cations to the Al 6 O2− anion. The electronic structures of Al 6 O2− core also accord with the Wade-Mingos rule. We build two typical ionic AB 2 crystals. The interactions between the building units reach 1.48 eV, and the phonon dispersion curves and elastic constants confirm the assembled structures are dynamically stable. [ABSTRACT FROM AUTHOR]