On the Constant Pressure Specific Heat C_P of a Simple Fluid

Abstract

Calculation of C_P from a model soft-core equation of state reveals a line in the phase diagram on which C_P is equal to its zero pressure value C _{P 0} . This line commences on the temperature axis where the second virial coefficient has a point of inflexion. At higher temperatures (and pressures) C_P falls below C _{P 0} . The detailed behaviour of C_P is presented via contour maps, illustrating the effects of changing the exponent N(= 3/n, where n is the repulsive potential exponent) which parameterizes the model. For soft-core fluids at high temperatures C_P deviates only slightly from the ideal gas value over a wide range of temperature and density, in marked contrast to the behaviour of hard-core models.