Nd-Co-B compound only 'converging' to paramagnetic ground state!
Posted: Mon Aug 24, 2020 5:53 pm
Hello everyone,
I am trying to calculate the magnetic ground state of a Nd-Co-B compound for which we have experimentally observed magnetic ordering. We suspect that the Nd and Co atoms are ordering antiferromagnetically with respect to each other, leading to a ferrimagnet overall (there is a 1:2 ratio of Nd:Co plus the difference in number of unpaired electrons for these atoms makes this seem likely to us).
I have been attempting to run spin-polarized calculations to see if this or some other model makes sense. However, I'm running into a big issue: if I use the Nd_3 PBE pseudopotential, the calculation always converges to a paramagnetic ground state. This happens no matter how I start my calculation (I've tried large MAGMOMs, smaller ones, a completely ferromagnetic model, only ordering in the Co atoms, and Nd/Co atoms ordered AFM to each other). I've tried this both with and without soc, but still always get a paramagnetic ground state. If I use the Nd PBE pseudopotential, the calculations don't converge. When my calculations reach the end of their iterations, they are not converged but do have magnetic moments on the atoms. Again, I've tried this both with and without soc.
Does anyone have any suggestions for how to deal with Nd correctly - I suspect that it is the cause of these difficulties, so any advice would be helpful. I can also provide more calculation details if that would be helpful.
Thanks!
I am trying to calculate the magnetic ground state of a Nd-Co-B compound for which we have experimentally observed magnetic ordering. We suspect that the Nd and Co atoms are ordering antiferromagnetically with respect to each other, leading to a ferrimagnet overall (there is a 1:2 ratio of Nd:Co plus the difference in number of unpaired electrons for these atoms makes this seem likely to us).
I have been attempting to run spin-polarized calculations to see if this or some other model makes sense. However, I'm running into a big issue: if I use the Nd_3 PBE pseudopotential, the calculation always converges to a paramagnetic ground state. This happens no matter how I start my calculation (I've tried large MAGMOMs, smaller ones, a completely ferromagnetic model, only ordering in the Co atoms, and Nd/Co atoms ordered AFM to each other). I've tried this both with and without soc, but still always get a paramagnetic ground state. If I use the Nd PBE pseudopotential, the calculations don't converge. When my calculations reach the end of their iterations, they are not converged but do have magnetic moments on the atoms. Again, I've tried this both with and without soc.
Does anyone have any suggestions for how to deal with Nd correctly - I suspect that it is the cause of these difficulties, so any advice would be helpful. I can also provide more calculation details if that would be helpful.
Thanks!