Structural and Electronic Properties of LaSi ( = 2-6) Clusters: Anion Photoelectron Spectroscopy and Density Functional Calculations.

The structures and electronic properties of LaSi ( = 2-6) anions and their neutral counterparts were investigated by anion photoelectron spectroscopy and theoretical calculations. The vertical detachment energies of the most stable structures of LaSi ( = 2-6) were measured to be 1.28, 1.58, 2.30, 2.05, and 2.91 eV, respectively. The lowest-energy isomer of LaSi is an isosceles triangle with a symmetry. For LaSi clusters, the most stable isomers are polyhedrons with La atom face-capping the Si frameworks. The lowest-energy structures of neutral LaSi clusters are similar to their anionic counterparts. The most stable isomer of neutral LaSi is a planar structure with symmetry, which is different from the triangular pyramid structure of LaSi anion. The lowest-energy isomer of LaSi is a symmetric pentagonal bipyramid structure, while for neutral LaSi cluster, the structure is not the most stable one. The natural population analysis showed that there is electron transfer from La atoms to Si atoms in LaSi ( = 2-6). The ZZ tensor component in isochemical shielding surfaces and the anisotropy of the induced current density analyses indicate that the most stable isomer of LaSi has aromaticity.