[ase-users] ase.db and magnetic moments

[Steen Lysgaard]

Hi,

I am having some difficulty extracting the magnetic moment assigned to 
each atom in an atoms object from a .db file. I think the reason is that 
magmoms and initial_magmoms are mixed up during the whole 
atoms->dict->row->dict->atoms transformation. Consider the following:

 >>> from ase.db import connect
 >>> from ase.lattice.surface import fcc111
 >>> db = connect('magmom.db')
 >>> atoms = fcc111('Ni',(2,2,3))
 >>> atoms.set_initial_magnetic_moments([0.6 for _ in range(len(atoms))])
 >>> print atoms[0].magmom
0.6
 >>> db.write(atoms,keywords=['magmom'])
1
 >>> new_atoms = db.get_atoms(1)
 >>> print new_atoms[0].magmom
0.0
 >>> print new_atoms.get_initial_magnetic_moments()
[ 0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.]

Doing this:

Index: ase/db/core.py
===================================================================
--- ase/db/core.py    (revision 3638)
+++ ase/db/core.py    (working copy)
@@ -497,7 +497,7 @@
                    dct['positions'],
                    cell=dct['cell'],
                    pbc=dct['pbc'],
-                  magmoms=dct.get('initial_magmoms'),
+                  magmoms=dct.get('magmoms'),
                    charges=dct.get('initial_charges'),
                    tags=dct.get('tags'),
                    masses=dct.get('masses'),

fixes the exampleabove. But I am not sure that this will not mix up the 
differentiation between magmoms and initial_magmoms further.

Best regards,
Steen

-- 
Steen Lysgaard
Post doc
Department of Energy Conversion and Storage
Technical University of Denmark
-------------------------------------------
Frederiksborgvej 399, P.O. Box 49
4000 Roskilde
Mobile +45 5194 4886
stly at dtu.dk
http://www.dtu.dk