Geometric structures, stabilities and properties of V₂Si_n^–/0 (n=8~17) clusters

The study of silicon clusters has led to significant interest in transition metal atoms doped silicon clusters. In order to provide robust guidelines for future experimental and theoretical investigations of vanadium doped silicon nanomatrials, the geometric structures, stabilities and properties of V₂Si_n^-/0 (n=8~17) clusters were systemically studied using density functional theory. Firstly, the lowest and lower lying energy structures of V₂Si_n^-/0 (n=8~17) clusters were globally predicted using the CALYPSO (crystal structure analysis by particle swarm optimization) searching method via the particle swarm optimization algorithm. Geometry optimization at the B3LYP/6-311+G(d) level revealed that two vanadium atoms tend to form V₂ bonds encapsulated gradually into silicon cages with an increasing number of silicon atoms. Secondly, based on the lowest energy structures, calculations of the average binding energy, second order energy difference, and HOMO-LUMO gaps indicated that the V₂Si₁₂^-/0 clusters exhibit higher stability, respectively. In addition, magnetic properties analyses revealed that the total magnetic moment is zero for the closed-shell structures of V₂Si_n (n=8~17) clusters; However, the open-shell structures of V₂Si_n (n=8~17) clusters have magnetic moments with values of 1 μB. Upon polarizability analysis, V₂Si₈^-/0 clusters with the highest mean dipole polarizability possess stronger nonlinear optical properties. Furthermore, the simulated PES(photoelectron spectroscopy), IR (infrared), and Raman spectra can provide theoretical guidance for future experimental investigations. Finally, the lowest energy structures of V₂Si_n (n=8~17) clusters are stable thermodynamically. Moreover, the heat capacity at constant volume (C_v) increases with the increasing of temperature, and standard entropy (S) decreases with temperature increasing.