[gpaw-users] Ti atom GS convergence problem and wrong Magnetic moment

[Jess Wellendorff]

according to WebElements the Ti atom has two unpaired valence electrons 
in its ground state.
http://www.webelements.com/titanium/atoms.html

/Jess W.

Jakob Blomquist wrote:
> Another thing.
> For the same titanium atom in a box if I set hund=True and occupation = 
> FermiDirac(width=0.0, fixmagmom=True)
> I will get a text output like below: How come I get +2 in Magnetic 
> Moment for Ti using Hund's rule?
>
>
> *****************
>             Time      WFS    Density  Energy       Fermi  Poisson  MagMom
> iter:   1  15:15:06  +2.6              -317.47976   0      14       +2.0000
> iter:   2  15:15:07  +0.8              -360.61764   0                 
> +2.0000
> iter:   3  15:15:08  -0.3               -362.63939   0                  
> +2.0000
> iter:   4  15:15:16  +0.8   -0.1     -263.03619   0      10       +2.0000
> iter:   5  15:15:25  +1.1   -0.1     -14.93935     0      13       +2.0000
> iter:   6  15:15:33  +0.7   -0.6      6.01038       0      10       +2.0000
> iter:   7  15:15:40  +0.4   -0.8      0.46328       0       6        +2.0000
>
> *****************
>
> Dr Jakob Blomquist
> Associate Professor
> Dep. of Material Science
> IMP, School of Technology
> Malmo University
> SWEDEN
> +46(0)40 6657751
> jakob.blomqvist at mah.se
>
>
> On 10/17/2011 11:43 AM, Jakob Blomquist wrote:
>   
>> I'm having a surprisingly hard time with a simple Ti-atom.
>> The magnetic moment doesn't follow Hund's rule (should be a 3F2 state)
>> but end up with +4 if it converges at all.
>> It doesn't matter much if I run with PBC = True or not or if the box is
>> symmetric or not.
>>
>> Is this something known?
>>
>> scrip run e.g:
>>
>> *****************
>> from ase import Atoms, Atom
>> from gpaw import GPAW, FermiDirac, MixerSum
>> from ase.parallel import parprint
>>
>> Ti = Atoms('Ti')
>>
>> Ti.center(vacuum=6.)
>> #Ti.cell[1,1] += 1.0
>> #Ti.cell[2,2] += (-1.0)
>>
>> #mixer = MixerSum(beta=0.1, nmaxold=3, weight=1.0)
>> name = 'Ti'
>> calc = GPAW(txt=name+'.txt',
>>               basis='dz(dzp)',
>>               nbands=-4,
>>               h = 0.16,
>>               xc='PBE',
>>               hund=True,
>>               )
>>
>> Ti.set_calculator(calc)
>> e = Ti.get_potential_energy()
>>
>> *****************
>>
>> ASE rev. 3.5.0.2113
>> GPAW rev. 0.8.0.8008
>>
>>     
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>   

-- 
Jess Wellendorff Pedersen

ph.d student
Center for Atomic-scale Materials Design (CAMD)
Department of Physics
Technical University of Denmark (DTU)