# [Pw_forum] ev.x fitting problem

Stefano de Gironcoli degironc at sissa.it
Mon Apr 20 19:09:34 CEST 2015

```Energy in eV are wrong

stefano
(sent from my phone)

> On 20 Apr 2015, at 18:31, Xiao <yxiao.ysu at hotmail.com> wrote:
>
>
> As I am using the ev.x to fitting EOS on Pd. I got the wrong bulk modulus. Here is my procedure. Please  help me check what’s wrong with my fitting?
> input data in Å and ev.
>
> 3.7351  -1.455513098
> 3.8129  -1.5041846
> 3.8907  -1.527184909
> 3.9685  -1.530334715
> 4.0463  -1.51819883
> 4.1241  -1.4945274
>
>      Lattice parameter or Volume are in (au, Ang) > Ang
>      Assuming Angstrom
>      Enter type of bravais lattice (fcc, bcc, sc, noncubic) > fcc
>      Enter type of equation of state :
>      1=birch1, 2=birch2, 3=keane, 4=murnaghan > 2
> then I get the output file like below:
>
> # equation of state: birch 3rd order.  chisq = 0.3034D-10
> # a0 =  7.4514 a.u., k0 = 6726 kbar, dk0 =  5.51 d2k0 = -0.001 emin =   -1.53118
> # a0 =  3.94309 Ang, k0 = 672.7 GPa,  V0 = 103.430 (a.u.)^3,  V0 = 15.327 A^3
>
> #########################################################################
> # Lat.Par       E_calc        E_fit       E_diff    Pressure      Enthalpy
> # Ang             Ry           Ry            Ry        GPa           Ry
> #########################################################################
>   3.73510      -1.45551      -1.45551     0.00000     170.75       -0.43510
>   3.81290      -1.50418      -1.50418    -0.00000      89.34       -0.93621
>   3.89070      -1.52718      -1.52719     0.00001      30.14       -1.32358
>   3.96850      -1.53033      -1.53033    -0.00001     -12.29       -1.61843
>   4.04630      -1.51820      -1.51820     0.00001     -42.10       -1.83804
>   4.12410      -1.49453      -1.49453    -0.00000     -62.42       -1.99662
> ~
> The k0 here is 672.7GPa, it should be 180GPa more or less. And I fitted same data with another software, it gives me 167GPa.
>
>
> Thank you!!!
>
> best
> xiao
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20150420/ae2dd3d8/attachment.html>
```