[Wien] possible pressure-induced transition

[Stefaan Cottenier]

> Therefore, pressure-induced phases transition=(DeltaE)/(DeltaV) which
> DeltaE=E2-E1 ( Energy of two phases at optimized Volume) and
> DeltaV=V2-V1( Volume of two phases at optimized volume)
> Is it correct?

No. The phase transition does not happen from the optimized volume of 
phase 1 to the optimized volume of phase 2.

> usually in paper, they find possible pressure-induced phases transition
> by using Gibbs data.
> they find difference of Gibbs energy (DeltaG) from two phases and find
> the pressure which in it DeltaG=0.
> Can you guide me how i can do that?
> I know Gibbs=E + PV at zero-temperature.
> Can you guide me how i can find data (E,P,V) for gibbs calculations in
> WIEN2k.

You wrote almost the answer. Calculate a few E(V) data points for the 
first phase, fit a Murnaghan equation of state through them (x eosfit), 
and you have as a result (V, E, P)-data for the studied interval 
(case.outputeos, case.eosfit, case.eosfitb). From this, you can easily 
calculated the enthalpy H=E+PV. Repeat for the second phase, and see at 
which pressure the two enthalpy curves intersect.

Stefaan