Among the pathways to obtain thermodynamic properties from intermolecular forces, Fluctuation Solution Theory (FST) is uniquely powerful. Derivative properties such as isothermal compressibility, partial molar volume, and composition derivatives of the chemical potential are obtained by integration of the molecular total and direct correlation functions. These in turn can be integrated to give accurate densities and activities as they vary from well-defined standard states. Though successful macroscopic corresponding states correlations have been developed for FST properties for a wide variety of systems, obtaining them directly from molecular simulation has long been challenging. Small errors in the long-range behavior of the molecular correlation functions can yield highly inaccurate results.
Recently, we have established a methodology for constraining the long-range molecular correlations from molecular dynamics simulations. Robustness and accuracy, as well as improvements over existing techniques, have been obtained for a range of simple and complex pure and mixed fluids.
The presentation will describe the approach and its application to a variety of systems.