Thank you. But there is still a discrepancy for the following data set: 10.3 -54.420098694852939 10.4 -54.716135146323531 10.5 -54.894109787500000 10.7 -53.873787839705884 modified ev.x gives 10.46368, while the fitting is 10.52255.
On Wed, Jul 29, 2015 at 4:23 AM, Paolo Giannozzi <[email protected]> wrote: > Funny: one of the parameters of the fit is good for small unit cells, but > too small for larger cells. In line 162 of PW/tools/ev.f90, replace > deltapar(1) = 0.1d0 > with something larger: > deltapar(1) = 1.0d0 > should be sufficient. Thank you for noticing this > > Paolo > > On Tue, Jul 28, 2015 at 6:06 PM, anyy zsj <[email protected]> wrote: > >> This data set is actual calculated because I use a large supercell: >> 10.1 -48.570860572794118 >> 10.3 -49.368013045588235 >> 10.5 -49.714550792647060 >> 10.7 -49.667482497058820 >> 10.9 -49.305953287500003 >> But the fitting results are not compatible. >> >> 2015-07-28 12:01 GMT-04:00 Paolo Giannozzi <[email protected]>: >> >>> Please show me a set of data *produced by actual calculations* that >>> ev.x doesn't fit properly >>> >>> paolo >>> >>> On Tue, Jul 28, 2015 at 5:51 PM, anyy zsj <[email protected]> wrote: >>> >>>> Thank you very much! >>>> Sure it is angstrom. My concern is that with the same data, ev.x and >>>> the manual fitting give different results as shown above. So I believe >>>> something is there. >>>> The discrepancy is gone if I use a small lattice parameter. For >>>> example, if I scale the data by 1/3, both of them give the same results. So >>>> what's going on? >>>> >>>> 2015-07-28 11:44 GMT-04:00 Paolo Giannozzi <[email protected]>: >>>> >>>>> 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 >>>>> >>>>> _______________________________________________ >>>>> Pw_forum mailing list >>>>> [email protected] >>>>> http://pwscf.org/mailman/listinfo/pw_forum >>>>> >>>> >>>> >>>> _______________________________________________ >>>> 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 >>> >>> _______________________________________________ >>> Pw_forum mailing list >>> [email protected] >>> http://pwscf.org/mailman/listinfo/pw_forum >>> >> >> >> _______________________________________________ >> 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 > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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