Completion of the structural determination of and rationalization of the surface-structure sequence (2×1)→(3×3)→(4×4) formed on Cu(001) with increasing Li coverage

With increasing Li coverage, the surface structure of Cu(001) evolves as (2×1)→(3×3)→(4×4) at room temperature. We here report the detailed structure of the most complex (4×4) phase determined by a dynamical low-energy electron diffraction (LEED) analysis with symmetrized automated tensor LEED. This completes the solution of these structures and allows a rationalization of their formation. The unit cell of the (4×4) structure consists of four Li adatoms forming a square cluster located on top of islands of nine Cu atoms; the islands are separated and joined by rows of substituting Li atoms.