Physics of Hydrogen under great Pressure - The difficult...

Physics of Hydrogen under great Pressure
For the van der Waals regime we modify this so that P=RT/V becomes:
P = [RT/(v-b)] - a/v
2
This van der Waals equation of state has to be modified further once P>P
c
and T>T
c
(supercritical), to give:
The Dieterici equation of state near the critical point is complex so one often uses the simpler
Berthelot equation:
P = [RT/(v-b)] - a/Tv 2
which improves over the van der Waals equation. Thisr the van der Waals equation. This
Berthelot equation is often rewritten using reduced variables:
More complex, less physical and more accurate are the virial equations of state:
PV = RT(1 + b/V + c/V
2
+ d/V
3
.... )
and the Beattie-Bridgman equation:
PV = RT + B/V + C/V
2
+ D/V
3
+ .....
where B=B(T), C=C(T), D=D(T) etc.