No, you cannot compare energies with/without spin-orbit, they are different physics. You could optimize the volume after adding it in (not internal co-ordinates) and this would be reasonable to do.
2010/2/24 shamik chakrabarti <shamikphy at gmail.com>: > Dear?Laurence Marks Sir, > ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Thank you very much for your reply. > What we can do then.....we optimize both volume and coordinates including > spin polarization and GGA+U and take this as the optimized structure as far > as the theory is concerned. Then we take that structure and run one scf > including spin-orbit coupling too. If the energy is less than the minimum > energy obtained in volume optimization we can go with spin-orbit coupling or > otherwise not. But it may happen that the energy is less and the volume is > different (I don't know how much effect spin-orbit coupling will have on the > volume!!...atleast we have experience that spin polarization definitely > effects volume) then which volume we should accept as our optimized volume? > > On Wed, Feb 24, 2010 at 7:26 PM, Laurence Marks <L-marks at northwestern.edu> > wrote: >> >> Unless something has changed, forces are not implemented for >> spin-orbit correctly so you cannot do a force minimization with them >> (unless you do some tricks, i.e. minimize the enegy by hand not using >> the code). >> >> For spin/U the question is how large a difference does this make to >> the electron density -- if it is large then the positions/optimal >> volume will be very different. >> >> But...do not depair! If spin-polarized and U is a much better >> description of the physics and you do not have multiple magnetic >> states, convergence of a LDA+U (or GGA+U) calculation can be much >> faster than a LDA calculation which does not describe the physics >> well. This follows from the physics/math of mixing. >> >> N.B., this is also why using a small mixing term in a >> Broyden/Multisecant method does not do what most people think it does, >> conventional wisdom is incorrect or at most correct for Pratt mixing. >> (Also, large mixing terms do not do what people think they do!) In >> general this not the way to solve a badly convergent problem, the >> correct (only) solution is to improve the physical model. >> >> 2010/2/24 shamik chakrabarti <shamikphy at gmail.com>: >> > Dear Wien2k users, >> > ?? ? ? ? ? ? ? ? ? ? ? ? ? ?I have a question regarding volume >> > optimization >> > and force minimization. >> > If I do volume optimization and force minimization for non magnetic >> > calculation and then use that optimized volume and structural >> > coordinates as >> > input for the calculation of volume optimization and force minimization >> > including spin polarization, spin orbit coupling term and LDA+U term, >> > then >> > whether I get the correct optimized values for both volume and >> > coordinates >> > of the structure which really need those corrections? >> > If I want to do volume and coordinates optimization including those >> > correction terms from the begining then it will take a very long time. >> > But >> > if we do the optimization using non magnetic calculation to reach closer >> > to >> > the actual energy and force minima and then put those optimized >> > structure >> > for non magnetic calculation for the optimization of the structure >> > having >> > those corrections it may take lesser time to reach the actual minima. >> > But >> > whether we really get actual minima in this way? >> > The above two questions actually are the same questions. I am very sorry >> > for >> > that reapeating. Actually I want to make clear my intentions to the >> > wien2k >> > users. >> > Thanks in advance. >> > regards, >> > Shamik Chakrabarti >> > _______________________________________________ >> > Wien mailing list >> > Wien at zeus.theochem.tuwien.ac.at >> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> > >> > >> >> >> >> -- >> Laurence Marks >> Department of Materials Science and Engineering >> MSE Rm 2036 Cook Hall >> 2220 N Campus Drive >> Northwestern University >> Evanston, IL 60208, USA >> Tel: (847) 491-3996 Fax: (847) 491-7820 >> email: L-marks at northwestern dot edu >> Web: www.numis.northwestern.edu >> Chair, Commission on Electron Crystallography of IUCR >> www.numis.northwestern.edu/ >> Electron crystallography is the branch of science that uses electron >> scattering and imaging to study the structure of matter. >> _______________________________________________ >> Wien mailing list >> Wien at zeus.theochem.tuwien.ac.at >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > -- Laurence Marks Department of Materials Science and Engineering MSE Rm 2036 Cook Hall 2220 N Campus Drive Northwestern University Evanston, IL 60208, USA Tel: (847) 491-3996 Fax: (847) 491-7820 email: L-marks at northwestern dot edu Web: www.numis.northwestern.edu Chair, Commission on Electron Crystallography of IUCR www.numis.northwestern.edu/ Electron crystallography is the branch of science that uses electron scattering and imaging to study the structure of matter.