The internal energy is just the short-range correlation.
Also below Tc?
Yes.
Does it also hold if one defines J_ij up to more than one shell? E.g. do other correlation functions <SiSi+j> with j=[1..number of shells] not entering the internal energy?
We can add correlation measurements but that is lots of data and will slow down the code quote a bit. Do you actually need all correlations?
No, I thought about nearest-neighbor-correlation <SiSi+1> or something like that.
That is just the energy.
I have two more minor questions concerning the output: Is the susceptibility \chi given out by alps equivalent to \chi=\beta*(<m^2>-<m>^2)?
On any finite lattice actually <m>^2 is 0, and one would need to measure <|m|>^2. We actually only do \chi=\beta <m^2>, so that the estimate is valid only above Tc.
Would it be possible to measure also \chi below Tc (without large modifications within the code)?
Yes, we can do that.
Is it possible to make a snapshot (spin position+spin alignment) of the spin system at a certain time-step?
This is easily possible. In which format would you like to see the snapshot?
Wow :). I think any format would be ok, maybe a 6 column table x y z Sx Sy Sz?
Just for Heisenberg models or also for other models such as Ising or XY?
At the moment we are mostly interested in the Heisenberg model.
Thanks really a lot, I kindly acknowledge your help.
Best regards, Fritz Koermann
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