Configurational excitations and low-temperature specific heat of the Frenkel-Kontorova model

We study the specific heat due to configurational changes in a Frenkel-Kontorova model with a finite density of defects. This model provides an example of intermediate disorder related only to the diffusing ions. The results show that it is possible to obtain excitations with very low energy due to quasidegenerate configurations, but it is not possible to obtain a smooth distribution for these energies. The present model applied to the one-dimensional ionic conductor hollandite can very well describe the peak structure recently observed in the low-temperature specific heat.