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Title: On the Structure and Chemical Bonding of Si62- and Si62- in NaSi6- Upon Na+ Coordination

Photoelectron spectroscopy was combined with ab initio calculations to elucidate the structure and bonding in Si62- and NaSi6-. Well-resolved electronic transitions were observed in the photoelectron spectra of Si6- and NaSi6- at three photon energies (355, 266, and 193 nm). The spectra of NaSi6- were observed to be similar to those of Si6- except that the electron binding energies of the former are lower, suggesting that the Si6 motif in NaSi6- is structurally and electronically similar to that of Si6-. The electron affinity of Si6 and NaSi6 were measured fairly accurately to be 2.23 ± 0.03 eV and 1.80 ± 0.05 eV, respectively. Global minimum structure searches for Si62- and NaSi6- were performed using Gradient Embedded Genetic Algorithm followed by B3LYP, MP2 and CCSD(T) calculations. Vertical electron detachment energies (VDEs) were calculated for the lowest Si6- and NaSi6- structures at the CCSD(T)/6-311+G(2df), ROVGF/6-311+G(2df), UOVGF/6-311+G(2d), TD B3LYP/6-311+G(2df) levels of theory. Experimental VDEs were used to verify the global minimum structure for NaSi6-. Though the octahedral Si62-, analogous to the closo-form of borane B6H62-, is the most stable form for the bare hexa-silicon dianion, it is not the kernel for the NaSi6- global minimum. The most stable isomer of NaSi6- is basedmore » on a Si62- motif, which is distorted into C2v symmetry similar to the ground state structure of Si6-. The octahedral Si62- coordinated by a Na+ is a low-lying isomer and was also observed experimentally. The chemical bonding in Si62- and NaSi6- was understood using NBO, molecular orbital, and ELF analysis.« less
Authors:
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Publication Date:
OSTI Identifier:
882967
Report Number(s):
PNNL-SA-48283
3689; KP1303000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics, 124(12):Article No. 124305
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory