Liquid-vapor equilibrium and interfacial properties of square wells in two dimensions

Liquid-vapor coexistence and interfacial properties of square wells in two dimensions are calculated. Orthobaric densities, vapor pressures, surface tensions, and interfacial thicknesses are reported. Results are presented for a series of potential widths lambda* = 1.4, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5, where lambda* is given in units of the hard core diameter sigma. Critical and triple points are explored. No critical point was found for lambda* < 1.4. Corresponding states principle analysis is performed for the whole series. For lambda* = 1.4 and 1.5 evidence is presented that at an intermediate temperature between the critical and the triple point temperatures the liquid branch becomes an amorphous solid. This point is recognized in Armas-Perez et al. [unpublished] as a hexatic phase transition. It is located at reduced temperatures T* = 0.47 and 0.35 for lambda* = 1.4 and 1.5, respectively. Properties such as the surface tension, vapor pressure, and interfacial thickness do not present any discontinuity at these points. This amorphous solid branch does not follow the corresponding state principle, which is only applied to liquids and gases. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775342]