| Abstract
| - Photoelectron spectroscopy and ab initio calculations are used to investigate the electronic structure and chemicalbonding of Si5- and Si52- in NaSi5-. Photoelectron spectra of Si5- and NaSi5- are obtained at several photonenergies and are compared with theoretical calculations at four different levels of theory, TD-B3LYP,R(U)OVGF, UCCSD(T), and EOM-CCSD(T), all with 6-311+G(2df) basis sets. Excellent agreement isobserved between experiment and theory, confirming the obtained ground-state structures for Si5- and Si52-,which are both found to be trigonal bipyramid with D3h symmetry at several levels of theory. Chemicalbonding in Si5, Si5-, and Si52- is analyzed using NPA, molecular orbitals, ELF, and NICS indices. The bondingin Si52- is compared with that in the isoelectronic and isostructural B5H52- species, but they are found todiffer due to the involvement of electron densities, which are supposed to be lone pairs in the skeletal bondingin Si52-.
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