Dear ITensor users,

I am calculating correlation functions for a spin-1/2 zig-zag chain using DMRG. Most of the values I am getting are exactly what they should be but a few of them are all over the place. I increased the number of sweeps and the number the states kept in each sweep and depending on how I choose the number of states kept, the accuracy fluctuates but all in all more sweeps tends to more accuracy. However, when I decreased the value of desired truncation error, it didn't help. I am not sure if I am doing everything right and I will truly appreciate if you could help.

I understand that DMRG is a numerical approximation method and my results cannot be exactly what the theory predicts. I am just interested to know how I can control the parameters in my code so that I get the best accuracy. Even if the cost of computations increases significantly, that should not be a problem because I have access to a cluster.

Thanks in advance.

Regards,

Niraj