Ab initiomolecular-orbital study of structures and energetics of Si3H3 neutral and anion

Abstract

The geometric structures and isomeric stabilities of various stationary points in Si(3)H(3) neutral and its anion are investigated at the coupled-cluster singles, doubles (triples) [CCSD(T)] level of theory. For geometrical surveys, the basis sets used are of the Dunning's correlation consistent basis sets of triple-zeta quality for the neutral. To the anions, the Dunning's correlation consistent basis sets of double-zeta quality with diffuse functions are applied. For the three lower-lying anion isomers, the Dunning's correlation consistent basis sets of triple-zeta quality with diffuse functions (aug-cc-pVTZ) are also used. The final energies for the optimized stationary points are calculated at the CCSD(T) level of theory with the aug-cc-pVTZ basis sets. The basis sets of 6-311++G(3df,2pd) were also used for the lower-lying anion isomers. The Gaussian-2 method was performed only for the lower-lying anion isomers to clarify the relative stabilities. The global minimum neutral 1 (C(1):(2)A) has an unsymmetrical hydrogen-bridged bond; the conformer 2 in C(s) symmetry is a saddle point connecting the two equivalent isomers 1. Two lower-lying isomers (3 and 4) are also predicted within the energy range of 20 kJmol. In the anion, however, the conformer 4 (C(s):(1)A(')) with five formal valence electrons is a global minimum. Two more isomers (2 and 3) lie within 20 kJmol as in the neutral; the conformer 1 converts to the isomer 2. The quartets for the neutrals and diradical triplets for the anions were further studied; lower-lying quartets and triplets, competing with the corresponding doublet and singlet, respectively, were not found in the present systems. The vertical and adiabatic electron affinities of the global minimum neutral 1, producing the second lowest-lying anion isomer 2, amount to 2.18 and 2.35 eV, respectively, at the CCSD(T)/aug-cc-pVTZ level of theory. The electron addition to the third lowest-lying neutral isomer 4 produces the largest vertical electron affinities of 2.48 eV. The D(3h) structure, being the global minimum in the corresponding Si(3)H(3) (+) cation (trisilacyclopropenyl cation), converts to the isomer 8 (C(s)) or 11 (C(2)) due to the Jahn-Teller effect in the Si(3)H(3) neutral.

Gold as hydrogen: Structural and electronic properties and chemical bonding in Si3Au3+∕∕− and comparisons to Si3H3+∕∕−

“…7, which are the three lowest energy isomers identified for Si 3 H 3 0/− from extensive computational search in Ref. 27. Although numerous other isomeric structures have been located on the potential energy surfaces of Si 3 H 3 0/− , those are substantially higher in energy than 19-21.…”

“…Although numerous other isomeric structures have been located on the potential energy surfaces of Si 3 H 3 0/− , those are substantially higher in energy than 19-21. 27 One may roughly find the structural correspondence between Si 3 Au 3 − ͑Figs. 2 and 6͒ and Si 3 H 3 0/− ͑Fig.…”

“…And the three lowest energy structures of Si 3 Au 3 are also similar to those of Si 3 H 3 . 27 However, obvious structural differences exist between Si 3 Au 3 +/0/− and Si 3 H 3 +/0/− , primarily due to the tendency of Au for bridge bonding. For example, in isomer 19 for the hydride, hydrogen does not bridge to form a 3c-2e Si-H-Si bond, instead it develops strong interaction with one Si by bonding terminally.…”

“…26 A recent ab initio study has explored the potential energy surfaces extensively and identified numerous structural isomers for Si 3 H 3 and Si 3 H 3 − . 27 These prior studies on Si 3 H 3 +/0/− provide a solid background for the current work to further explore the Au/ H analogy. We investigated the structures and bonding in Si 3 Au 3 +/0/− using both anion photoelectron spectroscopy ͑PES͒ and density functional theory ͑DFT͒.…”

Covalent gold

“…It was found that there are three isomers competing for the ground state of Si 3 Au 3 À , as is the case for Si 3 H 3 À . 59 Extensive structural searches showed that the potential energy surfaces of the tri-silicon gold clusters (Si 3 Au 3 À , Si 3 Au 3 , and Si 3 Au 3 + ) are similar to those of the corresponding silicon hydrides. The lowest energy isomers for Si 3 Au 3…”