Hi all, I am using the DMRG application to get some results on the Heisenberg quantum spin chain. First of all I want to apologize in advance for any silly question I might write in the following (I am quite new to this kind of simulations).

Is there any easy way of changing the position of the additional sites and the dimension of the environment block? I would like to use periodic boundary conditions, and try something like |system| - |1| - |environment| - |1|.

As far as I understand the algorithm evaluate the entropy of the density matrix of system+site obtained tracing out environment+site. I consider the last sweeps as the left part grows in spite of the right one and vice versa, and I plot the entropy against the "system+1" length. Is that final-sweep-one a good estimate of the behaviour of entanglement entropy of a "system+1"-long bit of chain against the environment?