Dear users,
I cannot understand the magnitude of ALPS susceptibility.
If I have the chain, I get results in agreement with Bonner-Fisher (PR 135, A640 (1964)), if I take into account that the Heisenberg model in their paper is defined as 2J*S_i*S_j while in ALPS it is written as J*S_i*S_j and summation in both cases runs only once.
But than I plot the susceptibility for 3D structure (for that purpose I write my own graph) with the strong exchange along one direction (706 K) and two very small exchanges in two other directions (3.2 K and 4.6 K), I get the susceptibility about two times larger. I also run calculation with only one exchange along the chain (706 K) and two others equal 0, but the susceptibility is the same as in previous case (with three exchange interactions).
Can you please help me to find that I am doing incorrectly? As far as I understand if I have pure chain and if I have chains in 3D structure with exchange between the chains equal 0 I should obtain the same results (namely, Bonner-Fisher).
With best regards, Zlata.
PS I attached the files with different susceptibilities and my graph.