Modified UNIFAC (Dortmund) — predictive property package

The refined UNIFAC: a ¾-power combinatorial term plus temperature-dependent group interactions (Weidlich & Gmehling 1987 + Gmehling-group revisions). Markedly better than original UNIFAC in the DILUTE limit — mean infinite-dilution activity-coefficient error 16% vs 42% against experiment — which is the regime absorbers, trace removal and solvent selection turn on. About the same on bulk VLE, so it is offered, not defaulted.