A systematic study of the lattice dynamics of several (2 x 2) overlayers on Ni(100) led to the conclusion that the reconstruction of the nickel surface with a carbon overlayer was of the soft-phonon type. The reconstruction was driven by the freezing of the S1 nickel surface phonon.

Adsorbate-Induced Soft-Phonon Reconstruction of the Ni(100) Surface. T.S.Rahman, H.Ibach: Physical Review Letters, 1985, 54, 1933-5