Density Functional Tight Binding (DFTB) calculations are performed to study atomic arrangements and charge distribution of Si(0 0 1) surfaces with one Ge atom adsorbate. For these Ge/Si(0 0 1) systems, the initial height between the Ge atom and the surface, and the adsorption position being relative to the Si dimers on the surfaces, have influences on the stable structures of the Ge atom on the Si surface. Firstly, two reconstructed Si(0 0 1) surfaces including c(4 x 2) and p(2 x 2) are obtained. Then, the Ge atom is placed on these two reconstructed surfaces. The calculations show the following results. For these dimers formed on the two Si(0 0 1) surfaces, dimer's bond length, and the buckling angle between the dimer and the surface have apparent differences as well as the charge distribution of these two surfaces. The Ge atom prefers to be located at two positions of the dimer: the outside top position of one atom of the dimer and the bridge position of this dimer. In these systems, the Ge atom always loses charges, and the charge transfer is found between atoms of one Si dimer. The asymmetric deviation of the two atoms in the dimer greatly affects the structure and charge distribution of Ge atom and the dimer. (C) 2018 Elsevier B.V. All rights reserved.