I don’t really know what happens with the `dmrg` code, I think I could reproduce the using the ALPS tutorials and adding the parameter Gamma=1.

Just by looking at the local magnetization one sees a quite ugly non-symmetric curve.

I just tried to plugin the same parameters in the new MPS code `mps_optim`, and the result seems better. The parameters are attached.

It is not really about understanding the problem, but more a workaround. I hope it could help you!

Regards,

Michele