Abstract

We developed a method that is able to easily determine chemical potentials of mixtures just from equilibrium molecular dynamics trajectories. We benchmarked the method on binary Lennard-Jones, urea-water mixture, and NaCl-water solution. As another example, we computed the pressure-temperature phase boundary where diamond can form from hydrocarbon mixtures with different atomic fractions of carbon. Notably, we find a depletion zone where diamond formation is thermodynamically favorable regardless of the carbon atomic fraction, due to a phase separation mechanism. The cooler condition of the interior of Neptune compared to Uranus means that the former is much more likely to contain the depletion zone, which may help explain the Uranus-Neptune dichotomy.