The hole fraction evaluated through fitting PVT data into the Simha-Somcynsky equation of state (SSeos) is in accordance with the results of positron annihilation lifetime spectroscopy providing the size of individual free volume cells as well as the total free volume (5).
The Simha-Somcynsky equation of state (SSeos) can be written in the form of two coupled equations:
Then, the hole fraction h (V/[V.sup.*], T/[T.sup.*]) of the SSeos is obtained through the analytical expression (12), Fig.