GROUND-STATES OF ONE-DIMENSIONAL COMMENSURATE-INCOMMENSURATE TRANSITION MODELS WITH DOUBLE-WELL INTERACTIONS

Multiwell interparticle potentials are proposed as a mechanism for the occurrence of modulated phases. This is examined through two models w ith double-well interactions. For these systems, the effective potenti al method is reviewed and a certain process of calculation is emphasiz ed. To characterize the modulated phases, the winding number omega, an d the rotation number Omega are redefined. The method to recover the c hain of particles and calculate the value of omega is given. We find t hat the phase diagrams strongly relate to the period of the external p otential D. For each model, there is a threshold value in D, which equ als to the distance between the two minimum value points. Within diffe rent interval of D, the phase diagrams exhibit different behavior. The periodicity of the phase diagram and the difference between modulated phases with the same Omega are also discussed.