Hi Máximo, In my experience, especially when dealing with spinel LiMn2O4, you also need to address the Jahn-Teller instability induced by Mn3+. If you slightly distort the spinel unit cell then the two different Mn sites (formally 3+ and 4+) will naturally emerge during relaxation (of course, you need the right level of theory as Nicola said): Mn3+ sites will be in a tetragonally distorted octahedral environment and Mn4+ sites will be in a more octahedral environment. If you start from a high-symmetry unit cell, you can also try to break the initial high symmetry of the charge/spin density by manually distinguishing between the two Mn sites: just name one type of Mn let's say Mn1 and the other one Mn2 and then use the same pseudopotential for both. Then, you can initialize the magnetization to a different value for the two different species.
HTH Marton Voros -- Materials Science Division Argonne National Laboratory On Mon, Apr 17, 2017 at 8:45 AM, Nicola Marzari <[email protected]> wrote: > > > Indeed! At the very least, use DFT+U, and/or explore > hybrid functionals. DFT+U+V seems to be very promising, > but it's not in the code there. > > nicola > > > > On 17/04/2017 15:36, Ary Junior wrote: > > Hi, > > > > Search for "constrained DFT" and you will find some documents that would > > be useful for you, like this one > > > > http://theossrv1.epfl.ch/Main/OxidationStates > > > > Ary Ferreira > > > > FAPESP postdoctoral fellow > > UFSCar - Brazil > > > > On Sun, Apr 16, 2017 at 1:06 PM, Máximo Ramírez <[email protected] > > <mailto:[email protected]>> wrote: > > > > Dear, > > > > I'm interested in simulate metal oxide that has two different > > valence state (oxidation number) in the same compound. > > > > For example: > > > > Is well-known from experimental results that spinel compounds have > > Mn ions with valence +3 and +4, LiMn3+Mn4+O4. > > > > How can I simulate this behavior in QE? > > > > And also, How can I post-process the two atoms like were different? > > > > Thank in Advance! > > > > > > <https://www.researchgate.net/publication/245108648_Factors_ > affecting_Li_mobility_in_spinel_LiMn_2O_4-A_first- > principles_study_by_GGA_and_GGA_U_methods> > > -- > > Sincerely, > > > > Máximo Ramírez > > Research Assistant > > Nanotechnology Laboratory, INTEC > > Santo Domingo, Dominican Republic > > > > > > _______________________________________________ > > Pw_forum mailing list > > [email protected] <mailto:[email protected]> > > http://pwscf.org/mailman/listinfo/pw_forum > > <http://pwscf.org/mailman/listinfo/pw_forum> > > > > > > > > > > -- > > http://lattes.cnpq.br/8221674673413336 > > > > > > _______________________________________________ > > Pw_forum mailing list > > [email protected] > > http://pwscf.org/mailman/listinfo/pw_forum > > > > -- > ---------------------------------------------------------------------- > Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL > Director, National Centre for Competence in Research NCCR MARVEL, EPFL > http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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