On Tue, Jul 28, 2015 at 5:26 PM, anyy zsj <[email protected]> wrote:
> 1.4989396432 -6.0466776328 > 1.5430233198 -6.0795705718 > 1.5879629631 -6.0993455319 > 1.6804430727 -5.9859764266 > The first column is volume and the second energy with Ry. After ev.x I > input Ang, noncubic, 4, it gives me a results of 0.40 for minimal volume. > It is certainly wrong. > of course it is: ev.x assumes that the input data corresponds to a physical EOS. Your data isn't physical: the volume is way too small > > Another example for the below data: > 10.1 -48.570860572794118 > 10.3 -49.368013045588235 > 10.5 -49.714550792647060 > 10.7 -49.667482497058820 > 10.9 -49.305953287500003 > The first column is lattice constant with angstrom and the second energy > with Ry. > After ev.x I input Ang, sc, 4, it gives me 10.50369, while I get a > different value 10.57517 by fitting to the formula in PRB 28,5480 (1983) > of Murnaghan's equation.: > http://gilgamesh.cheme.cmu.edu/doc/software/jacapo/appendices/appendix-eos.html > sure that the first column is in angstrom and not a.u.? This is what I get assuming it is in a.u.: # equation of state: murnaghan. chisq = 0.5402D-05 # a0 = 10.5740 a.u., k0 =13776 kbar, dk0 = 4.17 d2k0 = 0.000 emin = -49.73649 # a0 = 5.59554 Ang, k0 =1377.7 GPa, V0 = ******* (a.u.)^3, V0 =175.197 A^3 note the small value of the |chi|^2 (chisq) of the fit Paolo I have tested many groups of data but the discrepancy is there for those > large lattice parameters. Does ev.x use another equation or something else > I have missing? Thank you very much. > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > -- Paolo Giannozzi, Dept. Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
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