Structure and stability of Si6Li6: Aromaticity vs polarizability

Detailed exploration of the Si6Li6 potential energy surface shows that the most stable form of such cluster is not planar, it is a tridimensional structure formed by a silicon tetrahedron interacting with a silicon dimer through four lithium atoms. In order to understand stability, both polarizability and aromaticity were used. Given that the most stable structure is non-planar, aromaticity evaluation is not easy. Gratifyingly, the minimum polarizability principle is satisfied.