Geometric And Electronic Structure Of The Ytterbium Silicon Mixed Clusters Of The Nature And Optical Nature Of The Study

Structural and electronic properties of the neutral and charged rare-earth Yb-doped Si_n (n=l-13) clusters have been investigated computationally by using the relativistic density functional method with generalized gradient approximation;meanwhile, optical properties of the most stable YbSi_n (n=2-13) have been systematically investigated by using time-dependent density functional theory.The geometric structures, stabilities, electronic and bonding properties of the neutral and charged YbSi_n (n=l-13) clusters have been successively investigated. The most stable structures and the corresponding evolutional rule of the YbSi_n clusters are obtained. Comparisons of the YbSi_n (n=l-13) with available theoretical results of transition-metal-doped silicon (TMSi_n) clusters are made. The optimized geometries indicate that the most stable YbSi_n (n=l-13) clusters keep basically the analogous frameworks as the low-lying Si_n+1 clusters except for YbSi₈ and YbSi₁0 clusters, the doped Yb always tends to occupy the surfaced-capped site of the most stable for the neutral and charged YbSi_n isomers;and the Yb atom in the lowest-energy YbSi_n (n=l-13) isomers is not a gradual sinking trend into the Si_n framework with the number of Si atom varying from 1 to 13. At the same time, the Si-Si interaction in YbSi_n isomers will determine the stable geometry of Si_n framework of YbSi_n clusters. However, compared with the YbSi_n clusters, the TM atom in the most stable TMSi_n (n=l-13) clusters prefers an increasingly sinking site. Specifically, as the number of Si atom varying from 1 to 13, the TM atom in the most stable TMSi_n clusters transfers gradually from convex, to flatness, to concave site. In addition, the frameworks of the most stable YbSi_n (n=l-8) clusters are similar to those of some TMSi_n clusters While the framework of the most stable YbSi_n (n=9-13) clusters deviates strongly from those of TMSin clusters. Therefore, the growth pattern of metal doped silicon clusters depends on the kind of doped metal.Compared with the neutral YbSi_n clusters, most of the corresponding YbSi_n⁺ andYbSin" structures keep basically similar frameworks except for the small geometrical changes, the serious deformations in geometries are found for 3b+, 4b+, 4c+, 5b+, 5c+, 6d+, 8a+, 9a+, 10a+, 13a+, 3b", and 5c' clusters. The relative stabilities are investigated in term of the calculated fragmentation energies, exhibiting that the YbSin, YbSin+ (n=2, 5, 8, 10,13), and YbSin"(n=2, 5, 8, 10, 12) clusters have enhanced stabilities, and have the large abundances in mass spectroscopy. It is surprising that the stabilities of the neutral YbSin clusters are in good agreement with those of the charged YbSin clusters. The calculated HOMO-LUMO gaps indicate that the YbSi2, YbSi7, YbSiio, YbSin, YbSi4+, and YbSi7' clusters have stronger chemical stabilities. The neutral and charged YbSin clusters exhibit a universal narrowing of the HOMO-LUMO gap as compared to the pure silicon clusters, and that the surfaced-capped Yb atom in the neutral and charged YbSin clusters obviously influence the HOMO-LUMO gaps of original Sin+i clusters;this finding exhibits that the chemical stabilities of the neutral and charged YbSin clusters are decreased when the Yb impurity is doped into Sin clusters. The above results indicate that structural, relative stable, and electronic properties of the YbSin clusters is little impacted by the removal or addition of the charge to the YbSin clusters, the population analysis manifest that the net MP and HC values for the Yb atom in the YbSin and YbSin+ (n=l-13) clusters are positive;the net MP and HC values of the Yb atom in the YbSin' (n=4-13) clusters are positive, while their values for the Yb in the YbSin" (n=l-3) clusters are negative due to distribution of the additional negative charge. Therefore, the charges of the neutral and charged YbSin clusters transfer from Yb atom to Sin atoms and the Yb atom acts as an electron donor.The optical properties of the most stable YbSin (n=2-13) have been systematically investigated by using time-dependent density functional theory with generalized gradient approximation and LB94 potential. The calculated result indicates that the optical spectra of the YbSin (n=2-6) clusters mainly localize at the visible region;meanwhile, the optical spectra of the YbSi:, YbSi4, and YbSi6 clusters also have found at the near IR region, however, the distribution of the spectra for these clusters are very little in the near IR region and their oscillator strengths also are veryweakened as compared to others. Compared with the spectra of YbSin (n=2-6) clusters, the whole spectra of YbSin (n=7-13) clusters shift to the near IR region, i.e., causing the red-shift except for YbSiio and YbSin clusters. The spectra of YbSiio clusters distribute at the region from green to red in the visible spectrum;and the spectra of YbSin clusters mostly localize at the region from yellow to red in the visible spectra. Therefore, the spectra of the lowest-energy YbSin (n=2-13) clusters mainly distribute to the region from visible spectrum to near IR spectrum.