I’m a everyday user of tenpy whose last update was 6th January.

I use the iDMRG method and the system is 1D spin-1 XXZ chain:

Code: Select all

```
model_params = dict(S=1, L=2, Jx=1., Jy=1., Jz=Jz, D=0, bc_MPS='infinite', conserve='best', verbose=0)
M = SpinChain(model_params)
product_state = ["up"] * M.lat.N_sites
psi = MPS.from_product_state(M.lat.mps_sites(), product_state, bc=M.lat.bc_MPS)
dmrg_params = {
'mixer': True,
'trunc_params': {
'chi_max': 200,
'symmetry_tol': 1.e-14,
'svd_min': 1.e-14
},
'max_E_err': 1.e-16,
'verbose': 1
}
```

I have

**two questions**

**Q1.**When the entanglement_entropy is plotted with respect to Jz, it is not continuous. (see Fig)

It is suddenly dropped in the vicinity of critical points (Jz~0.3, Jz~1.2).

In my opinion, This does happens is not related to the chi_max in trunc_params.

How to get the smooth curve?

Should I minutely tune some parameters in dmrg_params or trunc_params?

**Q2.**

When simulating the iDMRG method, ‘psi.get_SL(0).shape’ is not sometimes equal to ‘psi.get_SR(0).shape’

Is this fair? If not, How to make these equal?