{"id":12,"date":"2016-06-13T00:32:00","date_gmt":"2016-06-13T00:32:00","guid":{"rendered":"https:\/\/aamiddle.expressions.syr.edu\/?page_id=12"},"modified":"2016-06-15T12:35:23","modified_gmt":"2016-06-15T16:35:23","slug":"code","status":"publish","type":"page","link":"https:\/\/aamiddle.expressions.syr.edu\/?page_id=12","title":{"rendered":"Code"},"content":{"rendered":"
Ising model partition function and free energies<\/h5>\n

This code calculates\u00a0the partition function and free energies of the Ising model on a (periodic) square lattice, for arbitrary nearest neighbor couplings. The code can be used for ferromagnets as an example: plot the free energy, heat capacity, etc., as a function of temperature and system size. The code includes several simple application sets: timing of the code, domain wall energies for a few small samples, and reading off the density of states from the partition function. The code uses nested dissection to evaluate the Pfaffians. For moderate sized samples, it requires multi-precision arithmetic.<\/p>\n