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Ab initio Calculations Using Vasp Code

How to calculate the magnetic exchange parameter of Nickel Oxide NiO

We will calculate the J2 parameter which represents the superexchange coupling between the next nearest neighbors (dNi-Ni = 4.17 A)using the GGA+U method.

We need to do a ferromagnetic and antiferromagnetic calculations and calculate the J2 parameter through a formula.

Ferromagnetic calculation

POSCAR
NiO
4.17
1.0 0.5 0.5
0.5 1.0 0.5
0.5 0.5 1.0
2 2
Cartesian
0.0 0.0 0.0
1.0 1.0 1.0
0.5 0.5 0.5
1.5 1.5 1.5

  INCAR

NiO GGA+U AFM
SYSTEM = "NiO"

Electronic minimization
ENCUT = 450
EDIFF = 1E-4
LORBIT = 11
LREAL = .False.
ISTART = 0
ISYM = 0
NELMIN = 6

DOS
ISMEAR = -5

Magnetism
ISPIN = 2
MAGMOM = 2*2.0 2*0 # FM conf.

Mixer
AMIX = 0.2
BMIX = 0.00001
AMIX_MAG = 0.8
BMIX_MAG = 0.00001

GGA+U
LDAU = .TRUE.
LDAUTYPE = 2
LDAUL = 2 -1
LDAUU = 5.00 0.00
LDAUJ = 0.00 0.00
LDAUPRINT = 2
LMAXMIX = 4

   

KPOINTS

k-points
0
gamma
4 4 4
0 0 0

 

POTCAR

Download the pseudopotential file from this link nio_Jcoupl.tgz


/NiO_fm> vasp_std


The output for the OUTCAR file

 

1 F= -.19296856E+02 E0= -.19296856E+02  d E =0.000000E+00  mag=     4.0000

 

Antiferromagnetic calculation

We need to replace only line in the INCAR file

MAGMOM    = 2*2.0 2*0  # FM conf

  by 

MAGMOM    = 2.0 -2.0 2*0  # AFM conf.

 

/NiO_afm> vasp_std


The output for the OUTCAR file
1 F= -.19537598E+02 E0= -.19537598E+02  d E =0.000000E+00  mag=     0.0000

 

Calculation of J2

 EFM = -.19296856E+02 eV  = -19.296856 eV

EAFM = -.19537598E+02 eV = -19.537598 eV


J2 = (EFM - EAFM) / 12 = (  -19.296856 + ( -19.537598  ) )/12 


J2 =  0.02006183 eV = 20.06183 meV


The experimental value : J2 = 19.01 meV (Hutchings M. T., Samuelsen E. J., Phys. Rev. B 6, 9, 1972, 3447)

 

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