Structural Features of Medium-Sized Ge (n) (n=35, 40, 45, 50, 55 and 60) clusters

摘要

By performing extensive search of the "compressing liquid" strategy together with the "genetic algorithm" approach, at the level of tight-binding(TB) potential model, the low-lying isomers of medium-sized Ge (n) (n = 35, 40, 45, 50, 55 and 60) are achieved. The selected lower-energy candidates from TB calculations are then fully optimized by the accurate first-principles calculations, the best candidates are identified. We find that the best candidates of germanium clusters undergo a structural transition from the prolate shape to the spherical structure in our concerned size range. This just corresponds to the observation of germanium clusters in ion mobility experiments. Furthermore, we reveal that the vibration entropy contributed to the free energy of an isomer which is useful for understanding the stability of the cluster at finite temperatures. As a result, the stability of the low-lying candidates at zero temperature is maintained at finite temperatures. In addition, the size-dependent HOMO-LUMO gaps have been briefly discussed in this paper. Our findings should be useful for future experiment investigations.