Paolo, Thanks for the comment. Even with appropriately chosen cutoffs for the kinetic energy and charge density, the AFM solution is difficult to converge with PAW pseudopotentials (suggested from website). The system I was trying (FeSb2) is less complicated than Daniel’s system. I thought it was an isolated case, but now that Daniel is also having problems maybe there’s more to it.
Regards, David Guzman Brookhaven National Laboratory > On Feb 9, 2020, at 12:38 PM, Paolo Giannozzi <[email protected]> wrote: > > >> On Sun, Feb 9, 2020 at 3:36 PM David Guzman <[email protected]> wrote: > >> Not sure [...] if there are extra setting that should go along with those >> potentials. > > the only extra setting with USPP and PAW is that you may (and often, you > should) use a cutoff for the charge density (ecutrho), that differs from > 4*ecutwfc (default value). > > Paolo > > >> >>>> On Feb 9, 2020, at 9:10 AM, Daniel Kaplan <[email protected]> >>>> wrote: >>>> >>> >>> Hello All! >>> >>> I'm trying to calculate a system with a known AFM ground state. In the >>> attached example, I provide the input data I'm using for CuMnAs -- a >>> tetragonal anti-ferromagnet. >>> I've started on this project by first executing the examples, and >>> particularly FeO. >>> I tested this example against all sorts of variations: different >>> functionals, with/without U, and so on. Without any further tweaking, the >>> system always converged to the AFM ground-state, provided the initial >>> moments were also oriented in the AFM configuration. >>> >>> Which makes my failure in this (CuMnAs) system even more puzzling. Firstly, >>> without any constraints, the system does not converge to an AFM state. >>> 1. Using 'constrained_magnetization=total' leads to completely wrong >>> results, with a divergent "Magnetic field". >>> 2. A more-or-less sensible result can be obtained with >>> 'constrained_magnetization='atomic' (as shown), however, the resultant >>> magnetization is not altogether anti-ferromagnetic. Note that the system is >>> in general endowed with PT-symmetry. The resultant eigenvalues DO NOT show >>> this and you can also see the disparity in the magnetic moments of the Mn >>> atoms, as well as eigenvalue difference of more than 1meV for some bands >>> and k-points. >>> 3. This behavior is weakly dependent on lambda. I tried fiddling around >>> with the values. A certain increase worsens the results, then seems to >>> improve it, only to worsen again. What is a reason value for the >>> constraint, in your estimation? I take it to be 5% of the unperturbed >>> energy (i.e., energy without the constraint). >>> 4. Testing the exact same system on different software (VASP, in this >>> case), converged very well to the AFM state (i.e., PT symmetry was >>> recovered to less than 1meV). >>> >>> What am I doing wrong, therefore? >>> I would appreciate any advice. >>> Yours thankful, >>> Daniel Kaplan >>> Dept. of Condensed Matter Physics >>> Weizmann Institute of Science >>> <scf.in> >>> <scf.out> >>> _______________________________________________ >>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) >>> users mailing list [email protected] >>> https://lists.quantum-espresso.org/mailman/listinfo/users >> _______________________________________________ >> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) >> users mailing list [email protected] >> https://lists.quantum-espresso.org/mailman/listinfo/users > > > -- > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
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