Thermal stability and properties of silicon-germanium nanocrystals

Using first-principles calculations and ensemble theory, we have calculated the ground-state energy and electronic properties of Si x Ge 10-x H 16 nanocrystals, and analyzed their stability and properties at finite temperatures. We have determined the numerical correspondence between chemical potential and the proportion of element in Si x Ge 10-x H 16 . The probability of various structures appearing within Si x Ge 10-x H 16 nanocrystals depends on temperature and chemical potential environment. The influence of vibrational free energy, as investigated by theoretical computations, is also summarized. The research results show that vibrational free energy enhances the structure stability by the occupation of Ge atoms and results in a more concentrated distribution of the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital.