We have added two features for you that will be available soon in the next release:
1. if you define the parameter PRINT_SWEEPS=xxx then after xxx sweeps the configuration will be dumped, for 3D Heisenberg in 7 columns: the site index, then the spatial coordinates and then the spin components.
2. we also record the energy for each bond type. Bond type 0 will be the nearest neighbor correlation you wants, etc..
Matthias
On 21 Jul 2008, at 23:20, Fritz Koermann wrote:
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?
If they are in your model then they will contribute, but we don't have a model taking interactions to certain shells in ALPS. Is that the model you need?
Yes, I need such a model. I defined one using the lattice.xml based on a given 3d bcc cell. I built up an model including the first 10 interactions with edges starting from the center (0,0,0) to the nearest-neighbors in the corresponding shells. Now I would like to figure out how strong the short-range correlations contribute to the internal energy and, also, to the free energy respectively. For such reasons a short-order correlation function would be very interesting.
I have more physics questions: Concerning the free energy, is it possible to set the the magnetic entropy in the classical Heisenberg model to constant for T->0 in order to obtain the free energy via integration (over the internal energy)? Or should one better integrate over the heat capacity to get the entropy?
Best, Fritz Koermann
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