Geometrical stabilities and electronic properties of Sin (n = 12–20) clusters with rare earth holmium impurity: a density functional investigation

Abstract

HoSi_n (n = 12–20) clusters with different spin states have been systematically investigated by using density functional theory with the generalized gradient approximation. The total energies, growth-pattern and equilibrium geometries as well as the APT charges of the HoSi_n (n = 12–20) clusters are calculated. The relative stabilities in terms of the calculated atomic averaged binding energies and fragmentation energies are discussed, revealing that the cake-like HoSi_n (n = 16, 18, 20) clusters have enhanced stabilities. Furthermore, the highest occupied molecular orbital – lowest unoccupied molecular orbital (HOMO–LUMO) gaps of the HoSi_n (n = 12–17) are above 1.55 eV while HoSi₁₆ has the largest one (1.95 eV). Interestingly, the calculated dipole moments of the cake-like HoSi_n (n = 16, 18, 20) clusters are very small, corresponding to the global minima. According to the calculated APT charges of the Ho atom in the HoSi_n (n = 12–20) clusters, the contribution of charge-transfer to the stability of HoSi_n clusters is briefly discussed, manifesting that the charges in HoSi_n clusters transfer from the Si atoms to the Ho atom. Additionally, the optimized geometries show that the rare earth Ho atom is completely encapsulated into the centre of the Si frame at n = 15. This finding is in good agreement with the available experimental results.