Journal of Statistical Physics, Vol. 69, Nos. 5/6, 1992. p. 1047-1068.
We have studied the Frenkel-Kontorova (FK) model with Toda interactions. The phase diagram is found to be asymmetric due to the exponential form of the Toda interaction. The reflection symmetry observed in the standard FK model is broken here. The singularity spectrum and the generalized dimension are calculated and their dependence on the nonlinearity parameter is discussed. The critical exponents of the gap in the phonon spectrum, the correlation length, and the Peierls-Nabarro barrier are found to be the same as those in the standard FK model and are independent of the nonlinearity parameter.