[ALPS-users] question about spin susceptibility

Hi All, Sorry to bother, I have a question about spin susceptibility. In my problem, the total spin is not a good quantum number. If I apply exact diagonalization code, how do I obtain spin susceptibility? One thing you might suggest is to measure total spin Sz (say the applied magnetic field is along z direction), and calculate \chi approximated as (<S_z>_h - <S_z>_{h=0}) /h. Then how to ask ALPS to measure <S_z>? Same question for quantum monte carlo. Could anyone be kind to offer a help? Thanks, -- GANG CHEN Department of Physics U.C. Santa Barbara