Study on one-dimensional CI phase transition with triple-well interactions

To study modulated structures and commensurate-incommensurate (CI) transiti ons, we generalize the Frenkel-Kontorova model to the Frenkel-Kontorova-Dev onshire model where the interparticle interactions are the triple-well pote ntial. By use of the so called effective potential method, numerical soluti ons of the eigenvalue problem are used to work out the exact phase diagrams of W, a triple-well potential. According to the winding number omega and t he rotation number Omega, we analyze the periodicity of the phase diagram a nd find some complex but regular phase structures. These new structures res ult from the triple-well interatomic interactions. A series of new transiti on behaviors enrich the traditional understanding on the periodicity of CI transitions.