[Wien] zigzag potential interpretation

[Stefaan Cottenier]

Good morning Xavier,

These are the partial charges for the two different surface atoms, with spin-orbit:

:CHA001: TOTAL VALENCE CHARGE INSIDE SPHERE   1 =   5.7094    (RMT=  2.2200 )
:PCS001: PARTIAL CHARGES SPHERE =  1 S,P,D,F,PZ,PXY,,D-Z2,D-XY,D-X2Y2,D-XZ,YZ
:QTL001: 1.1585 3.0936 1.4519 0.0044 1.0202 2.0734 0.0000 0.2461 0.3659 0.2540 0.5857 0.0000

:CHA002: TOTAL VALENCE CHARGE INSIDE SPHERE   2 =   5.7094    (RMT=  2.2200 )
:PCS002: PARTIAL CHARGES SPHERE =  2 S,P,D,F,PZ,PXY,,D-Z2,D-XY,D-X2Y2,D-XZ,YZ
:QTL002: 1.1585 3.0936 1.4519 0.0044 1.0202 2.0734 0.0000 0.2461 0.3659 0.2540 0.5857 0.0000

And these are the partial charges for a cell suggested by sgroup, where the two surface layers are equivalent:

:CHA001: TOTAL VALENCE CHARGE INSIDE SPHERE   1 =   5.7094    (RMT=  2.2200 )
:PCS001: PARTIAL CHARGES SPHERE =  1 S,P,D,F,PZ,PXY,,D-Z2,D-XY,D-X2Y2,D-XZ,YZ
:QTL001: 1.1585 3.0936 1.4519 0.0044 1.0202 2.0734 0.0000 0.2461 0.3659 0.2540 0.5857 0.0000

As you see, there are no differences at all.

I'm confident that this result is correct, only I'm in doubt why. I would understand your reasoning for a free atom: spin-orbit along 001 or 00-1 would result in the same orbital occupations. No problem for a bulk solid either: if you flip the moment 180 degrees, the 'tip of the arrow' 'sees' the same environment in both cases. Yet I miss something for these bulk slabs: in one case, the tip of the arrow sees vacuum, in the other case it sees the underlying bulk. Why does that necessarily result into exactly the same orbital occupations? As sgroup/initso make these two surface layers equivalent, there must be a symmetry argument. And it's that one which I don't get.

Best,
Stefaan


Van: Wien [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] Namens Xavier Rocquefelte
Verzonden: dinsdag 2 januari 2018 21:31
Aan: wien at zeus.theochem.tuwien.ac.at<mailto:wien at zeus.theochem.tuwien.ac.at>
Onderwerp: Re: [Wien] zigzag potential interpretation


A piece of paper will be useful to discuss this point ;)

To my point of you, the picture is correct: Fe moment point inward and outward. However, I think that for a given direction (c direction) the 001 and 00-1 orientation will lead to inward and outward respectively, which will give the same spin moment and orbital moment. It is due to the fact that the SO-effect will split the 3d orbitals similarly for the 001 and 00-1 orientations. Doing two calculations with 001 and 00-1 magnetization direction will lead to reverse the Fe moment for a given surface, and thus you will have inward and outward, respectively.

In your calculations, you have both (inward and outward) for one magnetization direction due to the surface termination.

The only limitation I see here is related to the definition of the Fermi level which can lead to difficulties to properly distinguish the two surfaces. Would it be possible that here is the problem? Are the partial DOS exactly the same?

Best Regards

Xavier
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