  A stable core-shell structure with Ih symmetry, Au12@Au30, has been
investigated by first-principles calculations. It is composed of an icosahedron
core and an icosidodecahedron shell. The stability of the core-shell Au42
structure is verified by vibrational frequency analysis and molecular dynamics
NVT simulations. Both the frontier molecular orbitals and the spin density of
states show obvious s-d hybridization characteristics. The adaptive natural
density partitioning analysis demonstrate multi-center bonds, twenty 6-center
{\sigma} bonds ,and one 12-center {\sigma} bond, which are of great importance
for the core-shell structural stability. In this core-shell nanostructure,
there are also a large number of one-center valence lone electron pairs with
the characteristics of d-like orbitals, so that the proposed Au12@Au30 could be
used in medicine and catalysis fields.
