Estimation of J magnetic coupling: Difference between revisions
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''<u>Exercise :</u>'' Study the change of the 180° superexchange coupling J<sub>2</sub> between the next nearest neighbors (d<sub>Ni-Ni</sub> = 4.17 A) by varying the U<sub>eff</sub> value. The following equation J<sub>2</sub> = (E<sub>FM</sub> - E<sub>AFM</sub>) / 12 expresses the super exchange Ni-O-Ni coupling as a function of the energy difference of the | ''<u>Exercise :</u>'' Study the change of the 180° superexchange coupling J<sub>2</sub> between the next nearest neighbors (d<sub>Ni-Ni</sub> = 4.17 A) by varying the U<sub>eff</sub> value. The following equation J<sub>2</sub> = (E<sub>FM</sub> - E<sub>AFM</sub>) / 12 expresses the super exchange Ni-O-Ni coupling as a function of the energy difference of the ferromagnetic (FM) and antiferromagnetic (AFM) configurations. In this case, the superexchange coupling J<sub>1</sub> between the nearest neighbors is neglected. The theoretical results can be compared to the experimental one : J<sub>2</sub> = 19.01 meV (Hutchings M. T., Samuelsen E. J., ''Phys. Rev. B 6'', 9, '''1972''', 3447) | ||
---- | ---- | ||
*INCAR | *{{TAG|INCAR}} | ||
Magnetism | NiO GGA+U AFM | ||
{{TAGBL|SYSTEM}} = "NiO" | |||
Electronic minimization | |||
{{TAGBL|ENCUT}} = 450 | |||
{{TAGBL|EDIFF}} = 1E-4 | |||
{{TAGBL|LORBIT}} = 11 | |||
{{TAGBL|LREAL}} = .False. | |||
{{TAGBL|ISTART}} = 0 | |||
{{TAGBL|ISYM}} = 0 | |||
{{TAGBL|NELMIN}} = 6 | |||
DOS | |||
{{TAGBL|ISMEAR}} = -5 | |||
Magnetism | |||
{{TAGBL|ISPIN}} = 2 | |||
{{TAGBL|MAGMOM}} = 2.0 -2.0 2*0 # AFM conf. | |||
# {{TAGBL|MAGMOM}} = 2*2.0 2*0 # FM conf. | |||
Mixer | Mixer | ||
{{TAGBL|AMIX}} = 0.2 | |||
{{TAGBL|BMIX}} = 0.00001 | |||
{{TAGBL|AMIX_MAG}} = 0.8 | |||
{{TAGBL|BMIX_MAG}} = 0.00001 | |||
GGA+U | |||
{{TAGBL|LDAU}} = .TRUE. | |||
{{TAGBL|LDAUTYPE}} = 2 | |||
{{TAGBL|LDAUL}} = 2 -1 | |||
{{TAGBL|LDAUU}} = 5.00 0.00 | |||
{{TAGBL|LDAUJ}} = 0.00 0.00 | |||
{{TAGBL|LDAUPRINT}} = 1 | |||
{{TAGBL|LMAXMIX}} = 4 | |||
*KPOINTS | *{{TAG|KPOINTS}} | ||
<pre> | <pre> | ||
k-points | k-points | ||
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</pre> | </pre> | ||
*POSCAR | *{{TAG|POSCAR}} | ||
<pre> | <pre> | ||
NiO | NiO | ||
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---- | ---- | ||
Necessarely, the J magnetic coupling decreases with the increasing of the U<sub>eff</sub> value. To assess the obtained value, similar calculations could be done using a [[NiO HSE06|hybrid functional]]. | |||
== Download == | |||
[[Media:nio_Jcoupl.tgz| nio_Jcoupl.tgz]] | |||
---- | ---- | ||
[[Category:Examples]] | [[Category:Examples]] | ||
Latest revision as of 08:48, 11 April 2023
Description: Estimation of the J magnetic exchange coupling using the GGA+U method.
Switching off the symmetry (ISYM = 0) is often necessary to generate different magnetic configurations.
Exercise : Study the change of the 180° superexchange coupling J2 between the next nearest neighbors (dNi-Ni = 4.17 A) by varying the Ueff value. The following equation J2 = (EFM - EAFM) / 12 expresses the super exchange Ni-O-Ni coupling as a function of the energy difference of the ferromagnetic (FM) and antiferromagnetic (AFM) configurations. In this case, the superexchange coupling J1 between the nearest neighbors is neglected. The theoretical results can be compared to the experimental one : J2 = 19.01 meV (Hutchings M. T., Samuelsen E. J., Phys. Rev. B 6, 9, 1972, 3447)
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 = 2.0 -2.0 2*0 # AFM conf. # 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 = 1 LMAXMIX = 4
k-points 0 gamma 4 4 4 0 0 0
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
Necessarely, the J magnetic coupling decreases with the increasing of the Ueff value. To assess the obtained value, similar calculations could be done using a hybrid functional.