Free volume and cavity formation in molecular liquids

By considering the theory of cavity formation in molecular liquids we show that general relationships for the accessible volume notably outperform models based on molecular packing. We ascertain several useful correlations between the molecular properties and the values of the accessible and screened volumes, and demonstrate that ordinary liquids boil when the ratio of the accessible and free volumes reaches the same threshold value.

► Dependencies not bound with models give reliable values for accessible volume. ► The rules of changes in accessible and screened volumes are connected with properties of molecules. ► Boiling of a liquid occurs at the same ratio of accessible and free volumes at atmospheric pressure.