Prigogine-Defay ratio

The Prigogine-Defay ratio is given by (Ref. 2 Eq. 1):

$\Pi ={\frac {1}{VT}}\left.{\frac {\Delta C_{p}\Delta k}{(\Delta \alpha )^{2}}}\right|_{T=T_{g}}$

where $V$ is the volume, $T$ is the temperature, $T_{g}$ is the temperature of the glass transition, $C_{p}$ is the isobaric heat capacity, $k$ is the compressibility and $\alpha$ is the thermal expansion coefficient.

References

1. I. Prigogine and R. Defay "Chemical Thermodynamics" Longman (1954) (out of print)
2. Jürn W. P. Schmelzer and Ivan Gutzow "The Prigogine-Defay ratio revisited", Journal of Chemical Physics 125 184511 (2006)
3. R. M. Pick "The Prigogine–Defay ratio and the microscopic theory of supercooled liquids", Journal of Chemical Physics 129 124115 (2008)