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How to calculate the enthalpy under different pressure

Posted: Thu Aug 18, 2011 6:29 pm
by bahadir.altintas
I need to calculate enthalpy for a system under various pressure between 0 to 600Gpa. I can optimize the systems under different pressures, but how can i calculate/get enthalpy of each system to plot enthalpy-pressure relation.

is it available at somewhere in output file of the optimizatim?

thanks

Re: How to calculate the enthalpy under different pressure

Posted: Fri Aug 19, 2011 12:30 pm
by jzwanzig
Can't you just add it by hand? I mean, given that H = U + pV, where U is the internal energy of the unit cell (etotal in the abinit output), p is your target pressure, and V the unit cell volume (ucvol in abinit output), can't you just calculate the pV contribution? (be sure to use consistent units, ucvol is in atomic units, therefore Bohr^3).

Re: How to calculate the enthalpy under different pressure

Posted: Fri Aug 19, 2011 4:27 pm
by bahadir.altintas
thank you for reply,

that is what i did yesterday but i though that could be an output gives for enthalpy. but i calculated greping volumes and pressures and Total energies from the outputs with the general enthalpy formula above.

bahadir