Numerical calculation on energy of static soliton solution for KdV equation

We calculated the energy of the static soliton solution of the KdV equation numerically by using the Hamiltonian density within the classical field approach. This approach can be used because the soliton solution is well-known analytically. We found the negative real energy that cannot be associated with a particle. Thus, this approach cannot be utilized to analyze the accumulated energy of the soliton in the KdV equation.