Thermodynamic factor of quaternary mixtures from Kirkwood–Buff integration

Expressions for the thermodynamic factor matrix Γ of quaternary mixtures are derived in terms of Kirkwood–Buff integrals and implemented into the massively parallel simulation tool ms2. To assess these expressions, a liquid-like supercritical quaternary Lennard–Jones mixture is sampled throughout its entire composition range, employing molecular dynamics in the canonical ensemble. Good agreement is found between numerical chemical potential derivatives and the results from the present Kirkwood–Buff integral expressions. Moreover, the limits of the thermodynamic factor matrix for pure, binary and ternary subsystems are discussed.