Study of structure, energy, and electronic properties of small-sized SixGey (x plus y=2-8) alloy clusters based on density functional tight binding calculations

The structural, energetic, and electronic properties of small-sized SixGey (x + y = 2-8) alloy clusters are studied by using the Density Functional Tight Binding (DFTB) method combined with unbiased structure optimization using a genetic algorithms (GAS) method. The results demonstrate a strong dependence of all properties not only on cluster size but also on cluster composition. In general, the Si atoms prefer to be closer to the center of the cluster (defined as the arithmetic average of all nuclear positions), whereas the Ge atoms are further away from the center. Although it in general is difficult to identify particularly stable clusters containing more than one element, some SixGey clusters are found to be more stable. According to the Mulliken gross populations, an electron transfer from the Ge atoms to the Si atoms is observed, especially for the atoms most far from the center. (C) 2015 Elsevier B.V. All rights reserved.