Tricritical point compressed monolayers

The freezing transition from the reentrant fluid to the commensurate solid monolayer seems to be of first order at low temperatures and changes to a continuous transition at a tricritical point near 85 K. This interpretation of the heat capacity and compressibility data [112], however, needs further experimental confirmation, and the corresponding tricritical point shown in the phase diagram Fig. 51 as an open triangle is only tentative. There are also conflicting theoretical predictions concerning the order of the RF - CD transition [77, 78, 151, 260], and the present resolution of the calorimetric data [112] does not allow us to draw a firm conclusion in this respect. 

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