# [Pw_forum] ev.x fitting problem

Mon Apr 20 21:31:06 CEST 2015

```Oh, sorry, Stefano. my mistake.It is Ry I used here.Thank you for your kind reply!
bestxiao

From: degironc at sissa.it
Date: Mon, 20 Apr 2015 19:09:34 +0200
To: pw_forum at pwscf.org
Subject: Re: [Pw_forum] ev.x fitting problem

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  -1.4555130983.8129  -1.50418463.8907  -1.5271849093.9685  -1.5303347154.0463  -1.518198834.1241  -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 > 2then 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!!!
bestxiao  _______________________________________________
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