Dear Stefano, Yes! I used a fcc unit cell. It should have a factor 4. Thank you!!! But can you explain why there is a 4 times relation between fcc and sc? I don’t really understand why it happens.
best xiao > On 20 Apr 2015, at 22:09, stefano de gironcoli <[email protected]> wrote: > > Dear Xiao, > are you using the fcc unit cell (1 atom/cell) or the SC one (4 atoms/cell) ? > that would make a factor of 4 in your bulk modulus. > stefano > > On 20/04/2015 21:34, 杨潇 wrote: >> Dear All, >> >> Sorry for my mistake of previous email! It should be Ry I used. >> >> 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 Ry. >> >> 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. >> >> So Please Help Me What’s Wrong With My Fitting? >> >> Thank you!!! >> >> best >> xiao >> >> >> _______________________________________________ >> Pw_forum mailing list >> [email protected] <mailto:[email protected]> >> http://pwscf.org/mailman/listinfo/pw_forum >> <http://pwscf.org/mailman/listinfo/pw_forum> > _______________________________________________ > Pw_forum mailing list > [email protected] <mailto:[email protected]> > http://pwscf.org/mailman/listinfo/pw_forum > <http://pwscf.org/mailman/listinfo/pw_forum>
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