[Wien] possible pressure-induced transition(find DeltaG)

[MAHDI SALMANI HIRMAND]

Dear Prof. Blaha,
I am studying possible pressure-induced transition for some compounds.
stefaan guide me how i can calculate Gibbs energy and find the pressure.

He told me "you can easily calculated the enthalpy H=E+PV using case.eosfit and case.eosfitb. Repeat for the second phase, and see at which pressure the two enthalpy curves intersect."

i did it but the two enthalpy 
curves are almost the same and it is difficult finding the position 
which two enthalpy curves intersect.
usually in paper they find difference of enthalpy energy from two phases and 
therefore the pressure which in it DeltaG or DeltaH=0

i would like to use this method. but when i check case.eosfitb file for 
two phases i see the values of pressure are different for example
case1.eosfitb                case2.eosfitb
 V1    E1     8.4                 V2     E2     8.9

  "       "        8.1                  "         "       8.7

  "       "        8.01               "          "       8.5

                                           "          "       8.08
can you guide me how i can find DeltaG when the value of pressure are different?

Sincerely
Mahdi
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