The small silicon clusters Si, (n=2-10) and their anions:: structures, themochemistry, and electron affinities

The silicon clusters structures, electron affinities, and dissociation energies of the Si-n/Si-n(-) (n=2-10) species have been examined using seven hybrid and pure density functional theory (DFT) methods. The basis set used in this work is of double-zeta plus polarization quality with additional diffuse s- and p-type functions, denoted DZP + +. The geometries are fully optimized with each DFT method independently. Four different types of energy separations presented in this work are the adiabatic electron affinity (EA(ad)), zero-point vibrational energies (ZPVE) corrected EA(ad) (EA(zero)), the vertical electron affinity (EA(vert)), and the vertical detachment energy (VDE). The first Si-Si, dissociation energies D-e (Si-n -> Sin-1+Si) for Si-n, and both D-e (Si-n(-) -> Sin-1 + Si-) and (Si-n(-) -> Si-n-1(-)+ Si) for Si-n(-) species have also been reported. The most reliable adiabatic electron affinities, obtained at the DZP + + BPW91 level Of theory, are 2.16 (2.15) eV for Si2, 2.32 (2.32) eV for Si3, 2.24 (2.25) eV for Si-4, 2.51 (2.51) eV for Si-5, 2.11 (2.12) eV for Si-6, 2.06 (2.07) eV for Si-7,2.86 (2.85) eV for Si-8, 2.28 (2.28) eV for Si-9, 2.45 (2.46) eV for Si-10. (EA(zero) values are in parentheses). While BP86, B3P86 and BPW91 predict to the most reliable dissociation energies. The dissociation energies for Si-n -> Sin-1 + Si are predicted to be 3.26 (3.23) eV for Si-2, 3.96 (3.92) eV for Si-3, 4.39 (4.33) eV for Si-4, 3.68 (3.62) eV for Si-5, 4.12 (4.08) eV for Si-6, 4.07 (4.01) eV for Si-7, 2.76 (2.73) eV for Si-8, 4.28 (4.22) eV for Si-9, 4.33 (4.28) eV for Si-10 with error of 0.13 (0.16) eV (coffected with ZPVE in parentheses). And the dissociation energies of Si-n(-) -> Si-n-1(-) + Si are predicted to be 3.95 (3.92) eV for Si-2(-), 4.14 (4.11) eV for Si-3(-), 4.29 (4.24) eV for Si-4(-), 3.98 (3.92) eV for Si-5(-), 3.72 (3.68) eV for Si-6(-), 4.01 (3.96) eV for Si-7(-) 3.59 (3.54) eV for Si-8(-), 3.69 (3.63) eV for Si-9(-), and 4.51 (4.46) eV for Si-10(-). (c) 2005 Elsevier B.V. All rights reserved.