Effect of discrete breather ensembles on the heat capacity of nonlinear one-dimensional crystals.

Abstract

There are numerous works studying the processes of generation of crystal lattice defects due to the fact that this process is the root cause of a change in a set of properties of a material. An atom’s abandonment of the equilibrium state always takes place by overcoming potential barriers through a transition from a dynamic defect to a topological one. Examples of dynamic defects are fluctuations and discrete breathers. Experimental and molecular dynamics studies have confirmed that discrete breathers (DBs) can be excited in various crystal lattices, and when interacting with point defects, they can reduce the potential barrier to their migration. In this work, we model a nonlinear one-dimensional crystal with particles whose interaction is described by a linear interparticle and nonlinear local potential. DBs in quantities from 1 to 7 and with an oscillation amplitude from 0.5 to 3 were introduced into a crystal with a hard or soft type of nonlinearity. It was found that the number of DBs in the ensemble does not affect the change in heat capacity, but a dependence of the heat capacity on the specified amplitude of the DB oscillation was revealed. In the case of a soft (hard) type of nonlinearity, the value of the heat capacity increases (decreases) with increasing oscillation amplitude