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运用密度泛函理论的UB3LYP/LanL2DZ方法研究了无限长封装过渡金属Cd的棱柱型硅纳米管,并讨论了它们的总能量、原子平均结合能、Mulliken原子净布局、HOMO-LUMO能隙以及电偶极距.计算结果表明无限长封装Cd的四棱柱型硅纳米管基本保持管状结构,而相应的五棱柱型则发生严重畸变.它们的最低能结构都是自旋单重态.无限长封装Cd的五棱柱型硅纳米管中所有Cd原子的Mulliken原子净布局都为正,说明电荷是从Cd原子向Si原子转移,Cd原子是电荷的施体.而有趣的是相应的四棱柱型硅纳米管里两端的Cd原子的Mulliken原子净布局为正,即Cd原子是电荷的施体,但是中间的Cd原子的的Mulliken原子净布局却为负,即电荷由Si原子向Cd原子转移,Cd原子是电荷授体,Si原子是电荷的授体,出现了电子反转.计算的HOMO-LUMO能隙说明无限长封装Cd硅纳米管中五棱柱HOMO-LUMO能隙小于四棱柱型的HOMO-LUMO能隙,说明无限长五棱柱型Cd-Si纳米管的化学活性大于相应的四棱柱型Cd-Si纳米管,且它们的HOMO-LUMO能隙均小于1.5 eV,说明它们具有半导体特性.计算的电偶极矩结果显示,无限长封装Cd的硅纳米管中,五棱柱型的硅纳米管的电偶极距为2.084 Debye,而四棱柱型的电偶极距却为零,说明无限长封装Cd的硅纳米管中四棱柱型的是非极性的,而五棱柱型的则是极性的.
The UB3LYP / LanL2DZ method is used to study the infinitely long prismatic silicon nanotubes with transition metal Cd encapsulated. The effects of total energy, atomic average binding energy, net Mulliken atomic layout, HOMO-LUMO energy gap, Dipole moment. The calculated results show that the infinite prismatic silicon nanotubes with Cd encapsulated basically remain in the tubular structure, while the corresponding pentagonal prismatic ones undergo serious distortion and their lowest energy structures are all spin singlet states. The net layout of Mulliken atoms of all the Cd atoms in Cd pentagonal silicon nanotubes is positive, indicating that charge is transferred from Cd atoms to Si atoms and Cd atoms are charge donors. Interestingly, the corresponding prismatic silicon The net arrangement of Mulliken atoms of Cd atoms at both ends of nanotubes is positive, that is, the Cd atoms are charge donors, but the net arrangement of the Mulliken atoms in the middle Cd atoms is negative, that is, the charges are transferred from Si atoms to Cd atoms and Cd The atom is a charge donor and the Si atom is the donor of charge, which results in the electronic inversion. Calculated HOMO-LUMO Energy Gap Description The pentagonal HOMO-LUMO gap in infinite-length encapsulated Cd silicon nanotubes is smaller than that of the tetrahedral HOMO- LUMO energy gap , Indicating that the chemical activity of infinite pentagonal Cd-Si nanotubes is greater than that of the corresponding prismatic Cd-Si nanotubes and their HOMO-LUMO energy gaps are less than 1.5 eV, indicating that they have the semiconducting properties. The results of the polar moments show that the electric dipole moment of the pentagonal silicon nanotube is 2.084 Debye, while the electric dipole moment of the quadrangular prism is zero, indicating that the infinite Cd Silicon nanotubes in the four prism type is non-polar, while the pentaprism type is polar.