First-principles calculations of structure and electronic properties of aluminum doped by Ge, Sn and Pb

Based on the first-principles calculation of plane wave ultra-soft pseudo-potential technology, the geometrical properties, impurity formation energy and electronic structures of Al doped by Ge, Sn and Pb were investigated. The structures and energies of three doped systems indicate that the formation of Ge doped Aluminum is minimum and the structure is the most stable. The impurity formation of Ge is −2.4070 eV and the system will release maximum heat, while doping with Pb will absorb heat. What's more, compared with pure aluminum, the charge distributions of central aluminum, which directly surround the impurities, are transformed from square to triangle. And this phenomenon leads that there is no covalent bond between central aluminum along the [110] direction. The charge density differences illustrate the interaction between Al and M (M = Ge, Sn and Pb) is covalent bonding. The amount of accumulated electrons shows that the system of AlGe possesses the strongest covalent bonding, followed by AlSn and final by AlPb. So the stability of Al-M (M = Ge, Sn and Pb) is AlGe > AlSn > AlPb. Additionally, according to Mulliken population analysis, it has been found that due to the incorporation of impurities elements, there are stronger repulsive effects between AlI and the bonds between AlI and AlII is the most covalent.