How is the k (horizontal location for green dots) calculated?

I looked through the MATLAB code at https://nanohub.org/resources/9203 and it does not produce anything like the green dots plot. How is the k (which I take as the Bloch parameter) computed from the energy at points of resonance? Is that k simply the free-space k=sqrt(2mE)/hbar of an incident free electron of energy E?