The role of an accurate and self-contained method to determine the average Laplacian of the potential energy or mean force constant, <∇2U>, which is the most relevant quantity for the prediction of vapor pressure isotope effects in the monatomic gases series is demonstrated. It is found that the method is able to calculate <∇2U> over the entire liquid and gas phase ranges of a Lennard-Jones fluid, in excellent agreement with simulation data. In addition, it also predicts other thermodynamic properties in a self-consistent way.
- Distribution functions
- Molecular dynamics