The equilibrium geometries and energies of neutral BeSi(n) (n = 2-10) species and their anions have been studied at the highest level of Gaussian-3 (G3) theory. The results reveal that the ground-state structures of these clusters are Be-encapsulated in silicon cages with n >or= 8. The reliable adiabatic electron affinities of BeSi(n) have been predicted to be 1.68 eV for BeSi(2), 1.87 eV for BeSi(3), 2.33 eV for BeSi(4), 2.29 eV for BeSi(5), 2.11 eV for BeSi(6), 2.37 eV for BeSi(7), 2.95 eV for BeSi(8), 2.74 eV for BeSi(9), and 1.92 eV for BeSi(10). The dissociation energies of Be atom from BeSi(n), Si atom from BeSi(n), and Si atom from Si(n) clusters have also been calculated, respectively, to examine relative stabilities. The trend of stability of BeSi(n) changed with n is converse to that of Si(n) when n or= 8, the encapsulated Be atom in silicon cages not only results in an identical trend for stability of BeSi(n) and Si(n) but also improves the stability of Si(n) clusters.
The geometries, electronic structures and energies of small ScSi n species (n = 1-6) and their anions have been systematically investigated by means of the higher level of the ccCA-TM, G4, and G4(MP2) schemes. The global minima of these clusters have been presented. The global minima of neutral ScSi n (n = 1-6) and their anions are "substitutional structure" which is derived from Si n+1 by replacing a Si atom with a Sc atom. The adiabatic electron affinities for ScSi n have been estimated. Compared with limited experimental data, the average absolute deviations from experiment for ccCA-TM, G4, and G4(MP2) are 0.21 eV, 0.22 eV, and 0.25 eV, respectively. The dissociation energies of Sc atom from the lowest-energy structure of ScSi n clusters have been evaluated to examine relative stabilities. The electron affinities and dissociation energies predicted by ccCA-TM, G4, and G4(MP2) methods, especially for ccCA-TM and G4, differ little from each other. The agreement may indicate they are reliable.
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