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I?m trying to constrain noncollinear magnetic moments in VASP along orthogonal directions to compare the relative energetics (and dielectric functions) of various ferromagnetic configurations.

When I try to constrain all magnetic moments along a specific directions
the moments instead bleed into other directions.

I get identical results with a coupling LAMBDA = 5000 and LAMBDA = 1000000.

I?m using the default Wigner Seitz radius (RWIGS) from the POTCAR -- not sure if this is sufficient. However, I would think that the radius that VASP is integrating over to obtain the magnetization on a particular site should also be the same radius it uses to determine how much energy penalty is incurred from going ?against? the constrained magnetic moments.

How do I better constrain these moments? I've included my INCAR below and the resulting magnetization in the same format as MAGMOM.

Thanks!

========== INCAR ============
SYSTEM = LIO_H0
Startparameter for this run:
NWRITE =3
SYMPREC = 1e-6
PREC = Accurate medium, high low
ISTART = 0 job : 0-new 1-cont 2-samecut
ICHARG = 2 charge: 1-file 2-atom 10-const
EDIFF = 1E-4 stopping-criterion for ELM
EDIFFG = -5E-3
ENCUT = 400
NSW = 0 number of steps for IOM
IBRION = 1 ionic relax: 0-MD 1-quasi-New 2-CG
ISIF = 2 stress and relaxation

LORBIT = 11
ISMEAR = 0
SIGMA = 0.01
GGA = PE

NBANDS = 256
ALGO = Normal
LOPTICS = .TRUE.
CSHIFT = 0.1
NEDOS = 2000
EMIN = 0
EMAX = 15

LMAXMIX = 4
LDAU = .TRUE.
LDAUTYPE = 2
LDAUJ = 0 0 0
LDAUL = -1 -1 2
LORBMOM = .TRUE.

LPLANE = .TRUE.
NCORE = 8
LSCALU = .FALSE.
NSIM = 8

LSORBIT = .TRUE.
I_CONSTRAINED_M = 1
LAMBDA = 5000 ! or 1000000 for the second run
ISYM = 0

ENCUTGW = 150
LDAUU = 0 0 2
M_CONSTR = 120*0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0
MAGMOM = 120*0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0

========== resulting mag ============

MAGMOM = 120*0 0.222 0.36 0.0 0.222 0.36 -0.0 0.222 -0.36 -0.0 0.222 -0.36 -0.0 0.149 0.318 0.0 0.148 0.319 -0.0 0.148 -0.32 -0.0 0.148 -0.32 0.0

(identical result for LAMBDA = 1000000)

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