ev.x enforces a lower (1) and an upper (15) bound on the derivative of the bulk modulus. I don't remember where they come from, but I am quite sure that dK0/dP ranges between 4 and 6 and never becomes negative or very large
Paolo On Wed, Jul 29, 2015 at 5:24 PM, anyy zsj <[email protected]> wrote: > similar but not the same. The fitting parameter for V0 is 1165.10028469 > A^3, Bulk modulus is 808.33GPa and its derivative is -31.54200148. The > derivative is very different. > > On Wed, Jul 29, 2015 at 11:03 AM, Paolo Giannozzi <[email protected]> > wrote: > >> Which parameters do you obtain for V0 (equilibrium volume), K0 (bulk >> modulus), dK0/dP? >> >> Paolo >> >> On Wed, Jul 29, 2015 at 4:13 PM, anyy zsj <[email protected]> wrote: >> >>> 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 >>>> >>> >>> >>> _______________________________________________ >>> 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
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