In Aspen Plus, when an activity coefficient model or a cubic equation-of-state model is used, an empirical correlation method is used in parallel for calculating liquid density of both pure components and mixtures. This concept is extended to cover polymer and oligomer components and polymer mixtures in Aspen Polymers. The liquid molar default route uses the van Krevelen model or the Tait model to calculate the liquid molar volume of pure polymers, oligomers, and segments. The Rackett model is used to calculate the liquid molar volume of non-polymer components. The mixture liquid molar volume is calculated using the ideal mixing rule