spin orbital problem

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ktao
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Posts: 6
Joined: Fri Dec 22, 2006 9:48 am

spin orbital problem

#1 Post by ktao » Mon Jul 23, 2012 9:01 pm

Hi, everyone,

I want to calculate the magnetic anisotropy energy of a small cluster. I got a really very large MAE value. I doubt the results and suspect there is something wrong in my calculations.

I did MAE calculations as following:

1, I relaxed the structure of the cluster in which all spins are in a collinear configuration

2, I did a non-self consistent calculation with the relaxed structure using "ISPIN = 1 (non magnetic)", and got CHGCAR and WAVECAR files

3, Using saved CHGCAR and WAVECAR, I did a non-collinear calculation (without spin orbital coupling) and got new CHGCAR and WAVECAR files. My input file is as following:

ISTART = 1
NWRITE = 2 : verbosity

ICHARG = 11

ENCUT = 400
ADDGRID = .TRUE.
PREC = accurate : accuracy

NELM = 300 : maximum number of SCF iterations
NELMIN = 8 : minimal number of SCF iterations
NELMDL = -6 : number of non-SCF iterations
EDIFF = 1E-7 : criterion for SCF convergence
ISMEAR = 1 : Methfessel-Paxton smearing
SIGMA = 0.1 : sigma for smearing

NPAR = 1

GGA = PE
GGA_COMPAT = .FALSE.
VOSKOWN = 1

ALGO = Fast

ISPIN = 2
MAGMOM = 0 0 8 7.61 2.47 4 0 8 4 -7.61 2.47 4 -4.70 -6.47 4 4.70 -6.47 4 0 0 8 4.70 6.47 4 -4.70 6.47 4 -7.61 -2.47 4 0 -8 4 7.61 -2.47 4 0 0 8
LNONCOLLINEAR= .TRUE.
LORBIT = 10

NBANDS = 560

# LWAVE = .FALSE.
# LCHARG = .FALSE.

LREAL=.FALSE.

# AMIX = 0.2
# BMIX = 0.00001
# AMIX_MAG = 0.4
# BMIX_MAG = 0.00001
MAXMIX = 40

# Parameters for SOC
ISYM = -1
LMAXMIX = 6
# LSORBIT = .TRUE.
# LORBMOM = .TRUE.
# SAXIS = 0 0 1

# Ionic Relaxation
NSW = 0 : maximum number of ionic steps
EDIFFG = -1.0E-2 : maximal residual force in eV/Ang
IBRION = 1 : quasi-Newton optimization
ISIF = 0 : optimize ions, cell shape and volume

4, I performed a calculation including SOC with saved CHGCAR and WAVECAR from step 3. In the INCAR file I only changed following parameters with SOC calculations,

ISTART = 1
ICHARG = 11

LSORBIT = .TRUE.
LORBMOM = .TRUE.
SAXIS = 0 0 1


5, When the spin direction of the system is along z axis, I only made a small change by setting "MAGMOM = 0 0 8 0 0 8 0 0 8 ...".

As we know, the MAE of most clusters is in the range of 10 meV. However, my results are much larger than that. So, I suspect that there is something wrong in my calculations. Any advices is appreciated. Thank you in advance!

By the way, I put the cluster in a large enough box and did a Gamma point calculation with PBE.
Last edited by ktao on Mon Jul 23, 2012 9:01 pm, edited 1 time in total.

support_vasp
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Re: spin orbital problem

#2 Post by support_vasp » Thu Sep 12, 2024 8:34 am

Hi,

We're sorry that we didn’t answer your question. This does not live up to the quality of support that we aim to provide. The team has since expanded. If we can still help with your problem, please ask again in a new post, linking to this one, and we will answer as quickly as possible.

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