May kink solution to the nonlinear Klein–Gordon equation be classified as a soliton?

Existence of the soliton solution to the generalized sine–Gordon equation (also known as the Kryuchkov–Kukhar’ equation) is numerically studied. The equation can be used to describe propagation of electromagnetic waves in a graphene-based superlattice. Calculation errors related to implicit representation of the kink solution to the equation under study are estimated. Variations in the shapes of kinks that move in opposite directions are studied prior to and after collision. The results show that the kink solution is not a soliton.