[交流] 在线答疑:Wien2k的问题

I am using the latest WIEN2k_08.2 release on a unix platform.

I am attempting to calculate the eigenvalues for my system in the full
Brillouin zone. I wish to do so using LDA+U with S-O coupling.

I am running the execution commands in the following sequence as
recommended so that I may ramp up the U slowly: runsp_lapw save_lapw case
initso_lapw runsp_lapw -so save_lapw case runsp_lapw -so -orb

The question I have relates to a phrase in the UG on p.83 under the ORB
function: "The presence of such an orbital field may lower the symmetry. In
particular the complex version of LAPW1 must be used."

My question is, if the symmetry is lowered by the orbital field will the
code automatically detect this and run lapw1c? In my case.dayfile this is
not occuring for the -orb run:
    cycle 1         (Mon Aug 18 18:15:55 BST 2008)         (40/99 to go)

>   lapw0         (18:15:55) 4.580u 0.420s 0:06.08 82.2%        0+0k 0+0io 182pf+0w
>   orb -up         (18:16:01) 0.000u 0.000s 0:01.14 0.0%        0+0k 0+0io 98pf+0w
>   orb -dn         (18:16:03) 0.010u 0.010s 0:00.08 25.0%        0+0k 0+0io 0pf+0w
>   lapw1 -up (18:16:03) 352.730u 7.760s 6:02.01 99.5% 0+0k 0+0io 302pf+0w
>   lapw1  -dn          (18:22:05) 352.650u 7.660s 6:00.82 99.8%        0+0k 0+0io 0pf+0w
>   lapwso -up -orb (18:28:06) 177.240u 5.500s 3:05.50 98.5% 0+0k 0+0io
> 266pf+0w
>   lapw2 -c -up -so (18:31:11) 115.440u 3.340s 2:01.17 98.0% 0+0k 0+0io
> 239pf+0w
>   lapw2 -c -dn -so (18:33:13) 115.430u 3.500s 1:59.11 99.8% 0+0k 0+0io
> 0pf+0w
>   lapwdm -up -so -c (18:35:12) 5.250u 0.620s 0:07.51 78.1% 0+0k 0+0io
> 158pf+0w
>   lcore -up        (18:35:19) 0.050u 0.090s 0:01.60 8.7%        0+0k 0+0io 95pf+0w
>   lcore -dn        (18:35:21) 0.060u 0.080s 0:00.45 31.1%        0+0k 0+0io 0pf+0w
>   mixer         (18:35:22) 0.360u 0.410s 0:02.45 31.4%        0+0k 0+0io 139pf+0w
:ENERGY convergence:  0 0.0001 0
:CHARGE convergence:  0 0.0000 0

Otherwise how do I know if I need to direct lapw1c to run and how would I
do it?

When adding SO AND orb; the latter is added in lapwso, which is
"complex" anyway.

Still you have the symmetry which is compatible with a) your crystal
symmetry, and b) with the SO interaction (direction of magnetization).

There are cases (mainly rare-earth compounds), where you may want to
reduce the symmetry further (to get a "localized, atomic-like state",
which does not obey crystal symmetry. But this requires that you
"understand" the symmetries and their consequences (degeneracy of states).

thanks for the help. I am considering a system with 4f moments
and so further reductions of symmetry to allow for the formation of
atomic-like orbitals may be valid.

I am a bit unsure of the technical procedure to achieve this in Wien2k. If
I would like to reduce the system symmetry further after the steps
runsp_lapw save_lapw case initso_lapw runsp_lapw -so ie. after the
spin-orbit part has been added and before I start ramping up the U, how
would I go about it?

If I manually lower the symmetry group chosen in the .struct file then I
could just add the atoms into the unit cell manually that are not produced
by the remaining symmetry operations. Is this the logical way to approach
this?

Alternatively should I start the entire series of calculations with the
lower symmetry?

Usually one should keep as much symmetry as possible!

In general it can lead to all kind of unwanted results when one breaks
symmetry more than necessary.

Thus first check if you really have some symmetry, where some f-orbitals
would still be degenerate (like octahedral or tetrahedral or axial symmetry).

The most simple way to break symmetry is usually to introduce a slicght change in
oneof the positions, i.e. if one atom sits in a high symmetry position (like (0,0,0)),
move it to (dx,dy,dz), dx can be small (0.0001); run the initializations (init and initso)
and before the scf, you can change back the coordinates.

Originally posted by fansw1129 at 2008-12-2 20:42:
估计是编译器没有装好