[Pw_forum] enthlapy of a system

[Bipul Rakshit]

Dear Matteo,
Got your point and really thanks for the help.
Just one more question....
In scf run if we set tstress = .true., then we also get the pressure. And
also we have Etot and V, so can we calculate H taking those Etot and V ??

On Tue, Sep 2, 2008 at 11:02 AM, Matteo Cococcioni <matteo at umn.edu> wrote:

>
>
> Dear Bipul
>
> I think all you need to do is computing the equation of state for both
> phases. In other words you choose a series of lattice parameters (that
> may be different for the two phases) and compute the total energy for
> each of them. In this case for B1 (NaCl) and B2 (CsCl) you don't need to
> relax the atomic positions for each lattice parameter as you would do in
> general. Once you get E(V) for each of the phase, you can use the
> program ev.x to fit a Murnaghan or a Birch eq. of state in your data.
>  From the equation of state you have chosen you can compute the
> derivative P=-dE/dV at any V within the interval of your fit. This will
> be the pressure on your system. for every value of P
> you will have V and the corresponding E so you will be able to construct
> E+PV (enthalpy) for the values of P you have.
>
> hope this helps,
>
> Matteo
>
>
>
>
> Bipul Rakshit wrote:
> > Hello Everyone,
> > I want to calculate the enthlapy at different pressures of ScAs in B1
> > and B2 phase, so that i able to find the transition pressure. Can
> > anybody tell me the correct method to do that?
> >
> >
> > --
> > Bipul Rakshit
> > PhD Student,
> > Barkatullah University,
> > Bhopal 462026,
> > MP, India
> > ------------------------------------------------------------------------
> >
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-- 
Bipul Rakshit
PhD Student,
Barkatullah University,
Bhopal 462026,
MP, India
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