Correct detection of symmetries in magnetic systems
The purpose of this change is to detect all symmetries of the magnetic system correctly. Please refer to the related issue #269.
Atoms related by a proper or improper rotation (and possibly with a fractional translation) are now treated as same kind if they are represented by the same chemical symbol. For example, Fe1 and Fe2 are treated as same kind and the symmetry detection subroutines sgam_at and the function checksym will check whether their positions and magnetic moments are related by a symmetry allowed for the Bravais lattice. So if Fe1 and Fe2 are sit at the same Wyckoff position and their magnetic moments are also related by a magnetic symmetry operation, this symmetry operation is taken as a symmetry of the system.
After this fix, all symmetries are properly detected by the code and we can identify the magnetic space group from the QE output by using e.g. Bilbao Crystallographic Server. Here are some examples with the magnetic space group identified by the fixed code.
- MnF2 (collinear AFM): P4_2'/mnm' (136.499)
| MnF2 scf.in | Total energy (Ry) | Total force (Ry/Bohr) | Total stress (kbar) | Fermi energy (eV) | Absolute magnetization (Bohr mag/cell) | # of k points | Iterations |
|---|---|---|---|---|---|---|---|
| original scf.out_orig | -811.04412471 | 0.004631 | 2.31 | 6.2066 | 9.60 | 96 | 14 |
| fix scf.out_fix | -811.04412452 | 0.004631 | 2.27 | 6.2066 | 9.60 | 60 | 12 |
| nosym scf.out_nosym | -811.04412467 | 0.004631 | 2.33 | 6.2066 | 9.60 | 490 | 31 |
The total magnetization is (0.00,0.00,0.00) Bohr mag/cell for all cases.
- Mn3Ir (non-collinear AFM): R-3m' (166.101)
| Mn3Ir scf.in | Total energy (Ry) | Total force (Ry/Bohr) | Total stress (kbar) | Fermi energy (eV) | Absolute magnetization (Bohr mag/cell) | # of k points | Iterations |
|---|---|---|---|---|---|---|---|
| original scf.out_orig | -1587.02939841 | 0.000000 | -9.39 | 17.6775 | 8.51 | 172 | 26 |
| fix scf.out_fix | -1587.02939769 | 0.000000 | -9.34 | 17.6775 | 8.51 | 44 | 23 |
| nosym scf.out_nosym | -1587.02939848 | 0.000002 | -9.42 | 17.6775 | 8.51 | 343 | 37 |
The total magnetization is (-0.02,-0.02,-0.02) Bohr mag/cell for all cases.
- Mn3Sn (non-collinear AFM): P6_3'/m'm'c (194.268)
| Mn3Sn scf.in | Total energy (Ry) | Total force (Ry/Bohr) | Total stress (kbar) | Fermi energy (eV) | Absolute magnetization (Bohr mag/cell) | # of k points | Iterations |
|---|---|---|---|---|---|---|---|
| original scf.out_orig | -2605.23651161 | 0.016933 | -20.24 | 15.7969 | 19.13 | 39 | 54 |
| fix scf.out_fix | -2605.23651178 | 0.016814 | -20.18 | 15.7969 | 19.13 | 15 | 17 |
| nosym scf.out_nosym | -2605.23651138 | 0.016933 | -20.25 | 15.7969 | 19.13 | 125 | 70 |
The total magnetization is (0.00,0.00,0.00) Bohr mag/cell for all cases.
Please suggest any better way to do the same if you have any.
Minkyu Park
University of Ulsan, Republic of Korea