材料期刊网

To understand modulated structures and commensurate-incommensurate transitions, we generalize the Frenkel-Kontorova model to a diatomic chain in the presence of an external sinusoidal potential. For the classical ground states, the diatomic effects are reflected by the phase diagram and the phonon spectrum. For the quantum ground states, the diatomic effects are reflected by the distribution of atoms on the external potential, the phase diagram, correspondences between the ground states and the orbits of the area-preserving maps, the phonon spectrum, and the occurrence of a second critical point K-c' besides K-c at which a transition by breaking analyticity occurs. [S0163-1829(98)06325-5].