Potts models phase diagram

Phase diagram based on a four-state Ising-Potts model 626... 

Fig. 7. Mean-field phase diagram of the four-state Ising-Potts model (A/kB = 90 K, J lkB = 125 K). The high-spin (HS) phase, the low-spin (LS) phase, and the ferroelectric-ordered (FO) phase are shown. The arrow line corresponds to Jo/kB = — 36 K, appropriate to the [Mn(taa)] system.

Berker AN, Wortis M. Blume-Emery-Griffiths-Potts model in two dimensions phase diagram and critical properties from a position-space renormalization group. Physical Review B. 1976 14 4946-4963. DOI 10.1103/PhysRevB.14.4946. 

Also the tricritical 3-state Potts exponents (for a phase diagram, see fig. 28c) can be obtained from conformal invariance (Cardy, 1987). But in this case the standard Potts critical exponents are related to an exactly solved hard core model, namely the hard hexagon model (Baxter, 1980), and not the tricritical ones. The latter have the values crt = 5/6, = 1/18, Yt = 19/18, <5t = 20, ut = 7/12, rjt = 4/21,

tricritical exponents coincide (den Nijs, 1979). 

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