[QE-users] How ev.x calculate enthalpy?

[Paolo Giannozzi]

On Fri, May 8, 2020 at 10:07 AM Inna Nangoi <inna.nangoi at mmk.su.se> wrote:

2.93 GPa = 29.3 kbar (Ry/Bohr^3)
>

1 kbar is not  1 Ry/Bohr^3

Paolo

------------------------------
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of
> Stefano de Gironcoli <degironc at sissa.it>
> *Sent:* 08 May 2020 09:29:58
> *To:* users at lists.quantum-espresso.org
> *Subject:* Re: [QE-users] How ev.x calculate enthalpy?
>
>
> dear Inna,
>
>
>   in the output file energies and enthalpies are written in Ry, volumes in
> A^3 and pressures in GPa
>
>   in order to apply directly the enthalpy formula everything should be
> given with consistent units.
>
>   if you check the ev.f90 code (in PW/tools) there are unit conversion
> factors when using the pressure
>
>
> line 304:         epv(i) = etot(i) + p(i)*v0(i) / ry_kbar
>
>
>    and when printing the volume
>
>
> lines 350-352:
>
>           WRITE(iun,'(f8.2,2x,f12.5, 2x,f12.5, f12.5, 3x, f8.2,
> 3x,f12.5)') &
>               ( v0(i)*bohr_radius_angs**3, etot(i), efit(i),  &
>                etot(i)-efit(i), p(i)/gpa_kbar, epv(i), i=1,npt )
>
>
>    best
>
>
> stefano
>
>
> On 08/05/20 09:01, Inna Nangoi wrote:
>
> Hi,
> I can't figure out how ev.x calculate enthalpy. I checked the ev.f90 and
> found out that
> Enth(i)=Efit(i)+Pfit(i)*V0(i) is the enthalpy (Ry)
> But when I try to calculate by hand I don't reach the same value as
> reported in ev.x
> output file (see below) . For example, for V = 120.51
> Enth(i)=Efit(i)+Pfit(i)*V0(i)
> Enth(i)= -181.23265  + 2.93*120.51 = 171.86161
>
> What am I doing wrong?
>
> # equation of state: murnaghan.        chisq =   0.4329D-07
> # V0 =  996.51 a.u.^3,  k0 =   92 kbar,  dk0 =  4.10  d2k0 =  0.000  emin
> = -181.24780
> # V0 =  147.67  Ang^3,  k0 =   9.2 GPa
>
> ##########################################################################
> # Vol.        E_calc        E_fit       E_diff    Pressure      Enthalpy
> # Ang^3         Ry           Ry            Ry        GPa           Ry
> ##########################################################################
>   124.13    -181.23698    -181.23704     0.00005       2.34     -181.10397
>   120.51    -181.23265    -181.23269     0.00003       2.93     -181.07085
>
> Best
> Inna Nangoi
> Stockholm University /Universidade Federal de Juiz de Fora
>
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
> users mailing list users at lists.quantum-espresso.orghttps://lists.quantum-espresso.org/mailman/listinfo/users
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users



-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20200508/d36ab431/attachment.html>