Determining the Magnetic Anisotropy: Difference between revisions

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Description: Magnetocrystalline Anisotropy Energy
Description: Magnetocrystalline Anisotropy Energy determined non-self-consistently


The Magnetocrystalline Anisotropy Energy is determined by rotating all spins according to different directions. First of all, an accurate ([[PREC|PREC]] = Accurate, [[LREAL|LREAL]] = .False.) collinear calculation (using the vasp-std script) in the ground state has to be done because of the very low changes in measured energies (sometimes, it could be about the micro-eV). Next, the Spin-Orbit Coupling ([[LSORBIT|LSORBIT]] = .True. ; using the vasp-ncl script) is took into account non-self-consistently ([[ICHARG|ICHARG]] = 11) for several spin orientations. The number of bands has to be twice compared to a collinear run).
The Magnetocrystalline Anisotropy Energy is determined by rotating all spins according to different directions. First of all, an accurate ([[PREC|PREC]] = Accurate, [[LREAL|LREAL]] = .False.) collinear calculation (using the vasp-std script) in the ground state has to be done. Next, the Spin-Orbit Coupling ([[LSORBIT|LSORBIT]] = .True. ; using the vasp-ncl script) is taken into account non-self-consistently ([[ICHARG|ICHARG]] = 11) for several spin orientations. In most of cases, the changes in energies are very low  (sometimes, it could be about the micro-eV). The number of bands has to be twice compared to a collinear run).


To modify the orientation of the spins in the crystal, we consider the second approach describes [[SAXIS|here]]. For the [[MAGMOM|MAGMOM]]-tag, the total local magnetic moment is written according to the z direction (necessarily, the x and y-directions are equal to 0). The spin orientation [uvw] is defined by the [[SAXIS|SAXIS]]-tag in the Cartesian frame. The Magnetocrystalline Anisotropy Energy is calculated by orientating the spins in different directions and the following equation : E<sub>MAE</sub> = E<sub>[uvw]</sub> - E<sub>min</sub>, with E<sub>min</sub> the energy of the most stable spin orientation.
To modify the orientation of the spins in the crystal, we consider the second approach described [[SAXIS|here]]. For the [[MAGMOM|MAGMOM]]-tag, the total local magnetic moment is written according to the z direction (necessarily, the x and y-directions are equal to 0). The spin orientation [uvw] is defined by the [[SAXIS|SAXIS]]-tag in the Cartesian frame. The Magnetocrystalline Anisotropy Energy is calculated by orientating the spins in different directions and the following equation : E<sub>MAE</sub> = E<sub>[uvw]</sub> - E<sub>min</sub>, with E<sub>min</sub> the energy of the most stable spin orientation.




More details are available in the [[SAXIS|SAXIS]] and [[LSORBIT|LSORBIT]] pages.
More details are available in the [[SAXIS|SAXIS]] and [[LSORBIT|LSORBIT]] pages.
''<u>Exercise :</u>'' Determine the Magnetocrystalline Anisotropy Energy of NiO in a non self-consistent approach by orientating the spins along the following path : (2,2,2) --> (2,2,1) --> (2,2,0) --> ... --> (2,2,-6). Compare to the [[Including_the_Spin-Orbit_Coupling|self-consistent approach]].


----
----
*INCAR
*{{TAG|INCAR}}
<pre>
NiO MAE
  SYSTEM    = "NiO"
 
Electronic minimization
  PREC = Accurate
  ENCUT        = 450
  EDIFF        = 1E-7
  LORBIT        = 11
  LREAL        = .False.
  ISYM          = -1
  NELMIN        = 6
  #  ICHARG = 11
  #  LCHARG = .FALSE.
  #  LWAVE = .FALSE.
  #  NBANDS = 52
  #  GGA_COMPAT = .FALSE.


DOS
NiO MAE
  ISMEAR    = -5
  {{TAGBL|SYSTEM}}    = "NiO"
   
Electronic minimization
  {{TAGBL|PREC}} = Accurate
  {{TAGBL|ENCUT}}        = 450
  {{TAGBL|EDIFF}}        = 1E-7
  {{TAGBL|LORBIT}}        = 11
  {{TAGBL|LREAL}}        = .False.
  {{TAGBL|ISYM}}          = -1
  {{TAGBL|NELMIN}}        = 6
  #  {{TAGBL|ICHARG}} = 11
  #  {{TAGBL|LCHARG}} = .FALSE.
  #  {{TAGBL|LWAVE}} = .FALSE.
  #  {{TAGBL|NBANDS}} = 52
  #  {{TAGBL|GGA_COMPAT}} = .FALSE.
   
  DOS
  {{TAGBL|ISMEAR}}   = -5


Magnetism
Magnetism
  ISPIN    = 2
  {{TAGBL|ISPIN}}     = 2
  MAGMOM = 2.0 -2.0 2*0.0
  {{TAGBL|MAGMOM}} = 2.0 -2.0 2*0.0
  # MAGMOM    = 0 0 2 0 0 -2 6*0 # Including Spin-orbit
  # {{TAGBL|MAGMOM}}   = 0 0 2 0 0 -2 6*0 # Including Spin-orbit
  # LSORBIT      = .True.
  # {{TAGBL|LSORBIT}}       = .True.
  # SAXIS = 1 0 0 # Quantization axis used to rotate all spins in a direction defined in the (O,x,y,z) Cartesian frame
  # {{TAGBL|SAXIS}} = 1 0 0 # Quantization axis used to rotate all spins in a direction defined in the (O,x,y,z) Cartesian frame
   
Orbital mom.
  {{TAGBL|LORBMOM}} = T


Orbital mom.
Mixer
  LORBMOM = T
  {{TAGBL|AMIX}}      = 0.2
  {{TAGBL|BMIX}}      = 0.00001
  {{TAGBL|AMIX_MAG}}  = 0.8
  {{TAGBL|BMIX_MAG}}  = 0.00001


Mixer
GGA+U
  AMIX     = 0.2
  {{TAGBL|LDAU}}     = .TRUE.
  BMIX      = 0.00001
  {{TAGBL|LDAUTYPE}}  = 2
  AMIX_MAG  = 0.8
  {{TAGBL|LDAUL}}    = 2 -1
   BMIX_MAG  = 0.00001
  {{TAGBL|LDAUU}}    = 5.00 0.00
  {{TAGBL|LDAUJ}}    = 0.00 0.00
  {{TAGBL|LDAUPRINT}} = 2
  {{TAGBL|LMAXMIX}}   = 4


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


*KPOINTS
*{{TAG|KPOINTS}}
<pre>
<pre>
k-points
k-points
Line 66: Line 68:
</pre>
</pre>


*POSCAR
*{{TAG|POSCAR}}
<pre>
<pre>
NiO
NiO
Line 80: Line 82:
  1.5 1.5 1.5
  1.5 1.5 1.5
</pre>
</pre>
----
 
Firstly, a collinear calculation has to be done. The magnetic anisotropy is determined non-self-consistently by rotating all spins according to a defined direction [uvw].
== Download ==
== Download ==
[http://www.vasp.at/vasp-workshop/examples/4_3_NiO_LSDA+U.tgz 4_3_NiO_LSDA+U.tgz]
[[Media:nio_noSOC.tgz| nio_noSOC.tgz]]
 
----
----
[[VASP_example_calculations|To the list of examples]] or to the [[The_VASP_Manual|main page]]


[[Category:Examples]]
[[Category:Examples]]

Revision as of 07:13, 18 August 2020

Description: Magnetocrystalline Anisotropy Energy determined non-self-consistently

The Magnetocrystalline Anisotropy Energy is determined by rotating all spins according to different directions. First of all, an accurate (PREC = Accurate, LREAL = .False.) collinear calculation (using the vasp-std script) in the ground state has to be done. Next, the Spin-Orbit Coupling (LSORBIT = .True. ; using the vasp-ncl script) is taken into account non-self-consistently (ICHARG = 11) for several spin orientations. In most of cases, the changes in energies are very low (sometimes, it could be about the micro-eV). The number of bands has to be twice compared to a collinear run).

To modify the orientation of the spins in the crystal, we consider the second approach described here. For the MAGMOM-tag, the total local magnetic moment is written according to the z direction (necessarily, the x and y-directions are equal to 0). The spin orientation [uvw] is defined by the SAXIS-tag in the Cartesian frame. The Magnetocrystalline Anisotropy Energy is calculated by orientating the spins in different directions and the following equation : EMAE = E[uvw] - Emin, with Emin the energy of the most stable spin orientation.


More details are available in the SAXIS and LSORBIT pages.

Exercise : Determine the Magnetocrystalline Anisotropy Energy of NiO in a non self-consistent approach by orientating the spins along the following path : (2,2,2) --> (2,2,1) --> (2,2,0) --> ... --> (2,2,-6). Compare to the self-consistent approach. 

NiO MAE
  SYSTEM    = "NiO"
    
Electronic minimization
  PREC = Accurate
  ENCUT         = 450
  EDIFF         = 1E-7
  LORBIT        = 11
  LREAL         = .False.
  ISYM          = -1
  NELMIN        = 6
  #  ICHARG = 11
  #  LCHARG = .FALSE.
  #  LWAVE = .FALSE.
  #  NBANDS = 52
  #  GGA_COMPAT = .FALSE.
    
 DOS
  ISMEAR    = -5

Magnetism
  ISPIN     = 2
  MAGMOM = 2.0 -2.0 2*0.0
  # MAGMOM    = 0 0 2 0 0 -2 6*0 # Including Spin-orbit
  # LSORBIT       = .True.
  # SAXIS = 1 0 0 # Quantization axis used to rotate all spins in a direction defined in the (O,x,y,z) Cartesian frame
   
Orbital mom.
  LORBMOM = T

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 



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

Download

nio_noSOC.tgz

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