<div dir="ltr">Dear all:<br><br>We are trying to make a calculation on a hypothetical Gd system consisting of connected Gd tetrahedra, which, as units, would have the diamond structure. This structure would have the 3D version of the Kagomé lattice. The Gd-Gd interaction is antiferromagnetic. One possible arrangement is having all the magnetic moments pointing either towards the center or away of the center, so the crystal would have one tetrahedron with the moments pointing to the center and the next one pointing out, making an 'in-out' arrangement.<br>
<br>For this magnetic structure we tried a non-collinear calculation using a unit cell of four Gd atoms, with the magnetic moment of the top atom pointing up and that of the other three atoms pointing down. We expected that the down pointing moments would eventually end out pointing away from the center of the tetrahedron, in which case the magnetic moments would make an angle of 109 degrees between them. <br>
<br>But we have tried different initial values for the angle with respect to the z axis for these three atoms, and our problem is that the angles barely move at the end of the calculation. We've considered initial angles of angle1(i) = 100, 120 and 160° relative to the up-pointing moment but in each case the final value of that angle changes only slightly. Maybe the program is not optimizing this parameter?<br>
<br>We have read different posts in this forum concerning non-collinear magnetism, and we tried different values for the "degauss" and "k-points" parameters too, as indicated there. Our results are the same, though. So, is our non-collinear magnetic calculation working? Are we using the correct parameters?<br>
<br>Thanks in advance. Hopefully you can give us a piece of advice about our problem, which will be greatly appreciated. We're using Quantum Espresso version 5.0.2-d-mpi and below we included one of our input files using angle1(i) = 120°:<br>
<br><b>&control<br> calculation='scf',<br> pseudo_dir = './',<br> outdir='./tmp'<br> !verbosity = 'high',<br> prefix='Gd-piro-scf-noncol-v4',<br>/<br> &system<br>
ibrav= 5, celldm(1)=9.44863,<br> celldm(4)=0.5,<br> nat= 4, ntyp= 4,<br> ecutwfc = 30.0,<br> occupations='smearing', smearing='mp', degauss=0.02,<br> nosym=.TRUE.,<br> starting_magnetization(1)= 0.6<br>
starting_magnetization(2)= 0.6<br> starting_magnetization(3)= 0.6<br> starting_magnetization(4)= 0.6<br> angle1(1)=0.0<br> angle2(1)=0.0<br> angle1(2)=120.0<br> angle2(2)=0.0<br> angle1(3)=120.0<br>
angle2(3)=120.0<br> angle1(4)=120.0<br> angle2(4)=240.0<br> noncolin=.true.,<br> nbnd = 56,<br> /<br> &electrons<br> mixing_beta = 0.5<br> conv_thr = 1.0e-4,<br> /<br>ATOMIC_SPECIES<br> Gd1 1. Gd.pbe-mt_fhi.UPF<br>
Gd2 1. Gd.pbe-mt_fhi.UPF<br> Gd3 1. Gd.pbe-mt_fhi.UPF<br> Gd4 1. Gd.pbe-mt_fhi.UPF<br> ATOMIC_POSITIONS crystal<br> Gd1 0.5 0.5 0.5<br> Gd2 0.0 0.5 0.5<br> Gd3 0.5 0.0 0.5<br> Gd4 0.5 0.5 0.0<br>K_POINTS automatic<br>
12 12 12 1 1 1</b><br><br>And here's part of the output file, giving the final polar coordinates of the magnetic moments:<br><br><b> ==============================================================================<br> atom number 1 relative position : 0.0000 -0.0000 1.2247<br>
charge : 7.543134<br> magnetization : 0.000653 -0.001747 6.294888<br> magnetization/charge: 0.000087 -0.000232 0.834519<br> polar coord.: r, theta, phi [deg] : 6.294889 0.016974 -69.491031<br>
<br> ==============================================================================<br><br> ==============================================================================<br> atom number 2 relative position : -0.2500 0.1443 0.8165<br>
charge : 7.538805<br> magnetization : 5.399085 -0.003164 -3.202229<br> magnetization/charge: 0.716173 -0.000420 -0.424766<br> polar coord.: r, theta, phi [deg] : 6.277292 120.672421 -0.033581<br>
<br> ==============================================================================<br><br> ==============================================================================<br> atom number 3 relative position : 0.0000 -0.2887 0.8165<br>
charge : 7.535512<br> magnetization : -2.699082 4.673208 -3.200589<br> magnetization/charge: -0.358182 0.620158 -0.424734<br> polar coord.: r, theta, phi [deg] : 6.274368 120.670857 120.009226<br>
<br> ==============================================================================<br><br> ==============================================================================<br> atom number 4 relative position : 0.2500 0.1443 0.8165<br>
charge : 7.533559<br> magnetization : -2.695245 -4.673544 -3.200622<br> magnetization/charge: -0.357765 -0.620363 -0.424849<br> polar coord.: r, theta, phi [deg] : 6.272985 120.678693 -119.972156<br>
<br> ==============================================================================</b><div style="font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div>-- <br>Dr. Juan Manuel Ramirez de Arellano<div style>
email: <a href="mailto:radear82@gmail.com">radear82@gmail.com</a></div><div style>Facultad de Ciencias, Taller de Estado Sólido Computacional,</div><div style>Universidad Nacional Autónoma de México,</div>04510, Ciudad Universitaria, D.F., México.<div style>
<br></div><div style><br></div></div>