Moving discrete breathers in a Klein--Gordon chain with an impurity

We analyze the influence of an impurity in the movement of discrete breathers in Klein--Gordon chains. We observe that the moving breather can cross the impurity, can be reflected by it, or can be trapped originating a quasi-periodic breather. We find that resonance with a nonlinear localised mode centred in the impurity is a necessary condition in order to observe the trapping phenomenon, as a difference with the resonance condition with a linear localised mode when this problem is studied within the Nonlinear Schr\"{o}dinger Equation approximation.