It was found that both the diffusion activation energy Ea(D) and Ea(Sex) increased linearly with pressure and had the same slope (0.022eV/GPa) for liquid Al. The temperature and pressure dependence of the excess entropy was well fitted by the expression:

-Sex(T,P)/kB = a(P)+b(P)T+c(P)exp[Ef/kBT]

which together with the small ratio of Ef/kBT led to the relationship of excess entropy to temperature and pressure, Sex ≈ −cEf/T, where c was about 12 and Ef (= ΔE − PΔV) was the favourable energy. Therefore, there existed a simple relationship between Ea(Sex) and Ef i.e. Ea(Sex) ≈ cEf.

Diffusion Activation Energy versus the Favourable Energy in Two-Order-Parameter Model: a Molecular Dynamics Study of Liquid Al. Y.D.Li, Q.H.Hao, Q.L.Cao, C.S.Liu: Chinese Physics B, 2010, 19[8], 086104