[Wien] YCo5 magnetic anisotropy calculations with GGA+U on Co

[Samolyuk, German D.]

Dear colleagues,

I'm calculating magnetic anisotropy in YCo5 within GGA+U approach with U-J=0.08 Ry Co d-states, wien2k_19.

To obtain the MAE, K, value the fully self-consistent calculations were executed for in plane and along z-axis magnetic moment orientation. the self-consistency is important for case of GGA+U.
Three sets of calculations were executed 1) keep 8 symmetry operation  obtained for [100] moment orientation, 2) keep 8 symmetry operations obtained for [110] operations, 3) one E symmetry operation - full BZ integration.
The MAE energy is calculated 1) as total energy difference 2) as a difference of band structure energy, EBND.

Following results were obtained:
>1)
100 - 8 SYM OP:
nk=16x16x17-5000: K = 6.53575196338352 meV/fu
nk=18x18x20-7000: K = 6.49467997718602 meV/fu
nk=16x16x17-5000: K = 15.4869591999841 meV/fu - EBND
nk=18x18x20-7000: K = -5.33487200008267 meV/fu - EBND
>2)
[110] - 8 SYM OP:
16x16x17-5000: K = 6.56594401516486 meV/fu
18x18x20-7000: K = 6.47836000134703 meV/fu
16x16x17-5000: K = 23.350166399905 meV/fu - EBND
18x18x20-7000: K = 24.0896663999706 meV/fu - EBND
>3)
FBZ - 1 SYM OP:
16x16x17-5000: K = 6.48733603011351 meV/fu
18x18x20-7000: K = 6.45932000479661 meV/fu
16x16x17-5000: K = -23.4508200001642 meV/fu - EBND
18x18x20-7000: K = -14.726882399907 meV/fu - EBND

The total energy results for MAE, K, are well converged and insensitive to in-plane magnetization orientation.
While, K value calculated from band structure energy, EBND, behaved strange.
Expectedly, both ways of K calculation gives close result for regular GGA (the force theorem).

Do you know what is source of such irregular EBND difference behavior for GGA+U calculaions?

Thank you,

German


Dr. German D Samolyuk
Materials Theory Group
Materials Science & Technology Division
Oak Ridge National Laboratory
Post Office Box 2008
Oak Ridge, TN 37831-6138
(865) 241-5394
(865) 241-3650 (FAX)
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