A simple two-dimensional Potts model with vacancies is introduced. The phase transition between paramagnetic and ferromagnetic is located by simple symmetry arguments. It is shown that the transition has a continuous and a first-order segment, separated by a tricritical transition. The locus of the tricritical point is determined by a transformation of the partition sum into that of an O(n) model. At the tricritical point and at some of the critical points this Potts model is soluble. © 1991.
Nienhuis, B. (1991). Locus of the tricritical transition in a two-dimensional q-state Potts model. Physica A: Statistical Mechanics and Its Applications, 177(1–3), 109–113. https://doi.org/10.1016/0378-4371(91)90141-X