<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">Paolo,<div>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). <br>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.</div><div><br></div><div>Regards,</div><div>David Guzman</div><div>Brookhaven National Laboratory <br><div dir="ltr"><br><blockquote type="cite">On Feb 9, 2020, at 12:38 PM, Paolo Giannozzi <p.giannozzi@gmail.com> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><div dir="ltr"><div dir="ltr">On Sun, Feb 9, 2020 at 3:36 PM David Guzman <<a href="mailto:davgumo@me.com">davgumo@me.com</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto">Not sure [...] if there are extra setting that should go along with those potentials.</div></blockquote><div><br></div><div>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). <br></div><div><br></div><div>Paolo<br></div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto"><div></div><div><div dir="ltr"><br><blockquote type="cite">On Feb 9, 2020, at 9:10 AM, Daniel Kaplan <<a href="mailto:danielkaplan137@gmail.com" target="_blank">danielkaplan137@gmail.com</a>> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><div dir="ltr">Hello All!<div><br></div><div>I'm trying to calculate a system with a <b>known</b> AFM ground state. In the attached example, I provide the input data I'm using for CuMnAs -- a tetragonal anti-ferromagnet.</div><div>I've started on this project by first executing the examples, and particularly FeO. </div><div>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.</div><div><br></div><div>Which makes my failure in this (CuMnAs) system even more puzzling. Firstly, <b>without</b> any constraints, the system does not converge to an AFM state. </div><div>1. Using 'constrained_magnetization=total' leads to completely wrong results, with a divergent "Magnetic field".</div><div>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 <b>DO NOT</b> 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.</div><div>3. This behavior is <i>weakly</i> 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).</div><div>4. Testing the <b>exact</b> 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).</div><div><br></div><div>What am I doing wrong, therefore? </div><div>I would appreciate any advice.</div><div>Yours thankful,</div><div>Daniel Kaplan</div><div>Dept. of Condensed Matter Physics</div><div>Weizmann Institute of Science</div></div>
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Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu/quantum-espresso" rel="noreferrer" target="_blank">www.max-centre.eu/quantum-espresso</a>)<br>
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