KINKS IN THE KLEIN-GORDON MODEL WITH ANHARMONIC INTERATOMIC INTERACTIONS - A VARIATIONAL APPROACH

We consider the nonlinear Klein-Gordon chain including anharmonic interatomic interactions. We use a direct perturbation method and a variational approach to obtain the approximate kink solutions of the model in the continuum limit taking the phi-4 and sine-Gordon chains as particular examples. The kink critical velocity due to the cubic anharmonicity is found analytically. Some physically important parameters of the kink, such as its effective mass and energy, are calculated based on the approximate solution and the results are checked by numerical simulations. It is demonstrated that the variational approach yields very accurate rate results for the kink parameters.