Local effect of Na adsorption on Cu(111)

The local effect of Na adsorbed on Cu(111) at very low coverage is studied with the Density Functional Theory. We find that the Na atom and its three nearest neighbor Cu atoms tend to form a small cluster, with the Na effect on surface being localized. The Mulliken occupation, density of state, interatomic energy, and interorbital energy show that the electron transfer mainly occurs from the 2p and 3s orbitals of Na atom to the 3d and 4s orbitals of the nearest neighbor Cu atoms, with the formation of a bond with four components that have different energies. In the anti-bonding state region, the 2p state of Na plays a key role in the bond, while in the bonding state region, not only the 2p state of Na has a very significant contribution, but the 3s state (which is the outermost Na orbital) also contributes to the bond between Na and the Cu(111) surface.