Dear Stefano, thank you for your answer.
Converting the values I get:
2.93 GPa = 29.3 kbar (Ry/Bohr^3)
120.51 A^3 = 813.24 Bohr^3
P*V = 23827.932 Ry
E(fit) = -181.23269 Ry
enthalpy = -181.23269+23827.932 =23646,70536041 Ry
It is something very stupid that I can't see where am I doing wrong.
Another question is regarding the chisq , what should be a reasonable value?
Best
Inna
________________________________
From: users <users-boun...@lists.quantum-espresso.org> on behalf of Stefano de
Gironcoli <degir...@sissa.it>
Sent: 08 May 2020 09:29:58
To: users@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
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