Thermodynamically self-consistent theories of fluids interacting through short-range forces

The self-consistent Ornstein-Zernike approximation (SCOZA), the generalized mean spherical approximation (GMSA), the modified hypernetted chain (MHNC) approximation, and the hierarchical reference theory (HRT) are applied to the determination of thermodynamic and structural properties, and the phase diagram of the hard-core Yukawa fluid (HCYF). We investigate different Yuk awa-tail screening lengths lambda, ranging from lambda=1.8 (a value appropr iate to approximate the shape of the Lennard-Jones potential) to lambda =9 (suitable for a simple one-body modelization of complex fluids like colloid al suspensions and globular protein solutions). The comparison of the resul ts obtained with computer simulation data shows that at relatively low h's all the theories are fairly accurate in the prediction of thermodynamic and structural properties; as far as the phase diagram is concerned, the SCOZA and HRT are able to predict the binodal line and the critical parameters i n a quantitative manner. At lambda =4 some discrepancies begin to emerge in the performances of the different theoretical approaches: the MHNC remains , on the whole, reasonably accurate in predicting the energy and the contac t value of the radial distribution function; the SCOZA predicts well the eq uation of state up to the highest lambda values investigated. The GMSA and the MHNC underestimate and overestimate, respectively, the liquid coexistin g density, while the SCOZA and HRT yield liquid branches that fall between the two former theoretical predictions, although both appear to overestimat e the critical temperature somewhat. At higher lambda's the GMSA and MHNC b inodals further worsen, while the SCOZA appears to remain usefully predicti ve. In general, the predictions of all the theories tend to slightly worsen at low temperatures and high density. The determination of the freezing li ne, performed by means of a one-phase "freezing criterion" (due to other au thors) is not particularly satisfactory within either the SCOZA or the MHNC the GMSA prediction for the freezing line at lambda =7 and 9 is instead ab le to follow in a qualitative manner the pattern of the solid-vapor coexist ence line as determined through computer simulation studies.:The necessity of further assessments of the freezing predictions is also discussed. Final ly, versions of the GMSA, SCOZA, and HRT that can be expected to be more ac curate for interactions with extremely short-ranged attractions are identif ied. [S1063-651X(99)10911-5].