Hi,
I should have explained more accurate. Of course, there is translational symmetry; I meant that CNT cross section is not round anymore. I have attached a .cif file to show what I mean. I'm pretty sure you know how to visualize this structure, but for the ones who don't, they can use visualization softwares like VESTA
Kwant just does tight binding models where *you* provide the tight-binding parameters (these may come from discretizing a continuous Hamiltonian, or from a DFT calculation or whatever, Kwant is completely agnostic of this). This means that Kwant doesn't know anything about whether the CNT is "squashed" or not if you don't change the tight-binding model itself. Calculating the way in which such a deformation affects the tight-binding parameters is beyond the scope of Kwant and you would need to use a different tool to do this for you. Hope that clarifies, Joe