Constraining local magnetic moments

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Task

Constraining the local magnetic moments on an Fe dimer.

Input

POSCAR

Fe dimer                               
 1.00000000000000000
     8.0000000000000000    0.0000000000000000    0.0000000000000000
     0.0000000000000000    8.0000000000000000    0.0000000000000000
     0.0000000000000000    0.0000000000000000    8.0000000000000000
   2
Cartesian
 3.00  0.00  0.00
 5.00  0.00  0.00

INCAR

SYSTEM        = Fe dimer
ISTART        = 0
ISYM          = 0
LNONCOLLINEAR = .TRUE.
MAGMOM        = 0 0 3   0 0 3
VOSKOWN       = 1
LORBIT        = 11
  
! mix slowly when increasing LAMBDA 
# AMIX          = 0.1
# BMIX          = 0.00001
# AMIX_MAG      = 0.2
# BMIX_MAG      = 0.00001
  
# I_CONSTRAINED_M = 1
# RWIGS           = 1.0
# LAMBDA         = 10
# M_CONSTR        = 0 0 1  0 0 1
  • Symmetry is switched off (ISYM=0).
  • Initially moments for ferromagnetic calculation are initialized.

KPOINTS

k-points
0
Monkhorst Pack
  1   1   1
  0.  0.  0.
  • A single k point in the calculation is sufficient.

Calculation

  • By using the initial ferromagnetic initialization of MAGMOM = 0 0 3 0 0 3 we get the following magnetic moments in the OSZICAR file:
...
DAV:  20    -0.929676054634E+01   -0.26101E-03   -0.16780E-03    60   0.102E-01    0.537E-02
DAV:  21    -0.929679955346E+01   -0.39007E-04   -0.30319E-04    60   0.590E-02
   1 F= -.92967996E+01 E0= -.93047629E+01  d E =0.238900E-01  mag= -0.0006 -0.0003  6.0537
  • By using a different initial magnetization of MAGMOM = 0 0 3 0 2 2 the system converges to a ferromagnetic solution:
 magnetization (y)                          magnetization (z)
# of ion     s       p       d       tot   # of ion     s       p       d       tot
----------------------------------------   ----------------------------------------
  1        0.018  -0.001   1.071   1.087     1        0.045  -0.003   2.587   2.628
  2        0.019  -0.001   1.069   1.087     2        0.045  -0.003   2.588   2.629
----------------------------------------   ----------------------------------------
tot        0.037  -0.003   2.140   2.174   tot        0.089  -0.007   5.175   5.257

Download

4_5_Fe_dimer.tgz


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