Theoretical Study On The Electronic Structures Of Nonmetal Doped In Metal Clusters And Magic Structures

Aluminum based clusters have been of great scientific interest in the past 30years.For the binary Al-Na clusters,the aluminum cores with the valence electrons form?Al_n?^q-Zintl anions,the Na⁺cores are located on the peripheries and ironically bonded to the anions.By using genetic algorithm combined with B3LYP and QCISD methods,this paper investigates the stabilities and electronic structures of Al₆CNa_m?m=2,4,6,8?,Al₆OM_m?M=Na,K;m=2,4,6?and a few other Al_nXNa_m?X=C,N,O?clusters.The computations show that the C atoms prefer sitting at the center while the Na atoms tend to locate at the outside of the clusters.The valence molecular orbitals 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 subband.The 26 valence electrons in Al₆CNa₄ form closed 1S²1P⁶2S²1D¹⁰2P⁶ shells and correspond to a new magic structure.The molecular orbitals and electron localization function?ELF?show that the sodium cores are exposed at the outside of the valence electrons and form naked cations.The contraction of the valence electrons due to 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?^m-.The Al₆CNa₄ has a tetrahedral structure with symmetry T_d and it may be used as building blocks to synthesize Zintl solid.Experiments revealed that Al₇C^-shows pronounced thermal stability and chemical inertness.Here we analyze the electronic structures and present the proper interpretation for these magic clusters.For the Al₆OM_m?M=Na,K;m=2,4,6?and a few other Al_nXNa_m?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.Unbiased global search shows the nonmetal X atom is situated in the center of the magic clusters.The 2s/2p orbitals of the central atom interact strongly with the delocalized 1S/1P Jellium 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 S²P⁶ shells.The orbital interactions push up the 2S Jellium orbital to a high energy,but the 1D orbitals don't interact with other orbitals.So the 26 valence electrons form closed s²p⁶S²P⁶D¹00 shells.This electronic configuration can be taken as the combination of the octet rule and 18-electron rule,and corresponds to a strong magic number.The octahedral Al₆X^q-core is a superatom with great stability and chemical inertness,and it can be used as building blocks to assemble Zintl phase materials by interaction with alkali metals.