Dear Zhian

I'm making my first experiments with Alps... I want to use DMRG for ferrimagnetic chain,but i have some problems.

First,in the dmrg steps because the chain don't have the symmetry between left and right halves,the density matrices for these two halves should be constructed at every iteration of the calculation.

This is not quite right. You can use DMRG in disordered systems if you wish. Try it out as it is.

Second,I think that it isn't exist spin parity symmetry.

Sztot is a well defined quantum number in ferrimagnetic spin chains. You can determine the value for the ground state and use it as an input parameter.

I hope this helps. If you have further questions, it would be very helpful if you could direct us to a paper with the Hamiltonian written explicitly

Saludos, <ADRIAN>