Second variational method and effective screening medium |
- Date: 2023/06/02 22:58
- Name: Kirou Sankaran
<kirousankaran@duck.com>
- Dear,
In the study of voltage controlled magnetic anisotropy, I am studying CoFe|MgO|vacuum based magnetic tunnel junction stacks.
I have used both the second variational method and effective screening method (ESM1) together with applied electric field.
The 'single shot' magnetic anisotropy energies are compared with their full self consistent method counterpart (with ESM1).
I noticed that second variational method and ESM1 do not give similar values as the full self consistent method (several orders of magnitude off).
Here is the comparing table of MAE with ESM1 between 'single shot' and self-consistent method for different applied electric field:
Method Magnetic anisotropy energy (mJ/m2) VCMA coefficient (fJ/V.m)
-0.140 V/nm 0.000 V/nm +0.140 V/nm
Single-shot’ -1.011E+06 -9.477E+05 -9.058E+05 3.7E+08
Full SCF 2.805 2.819 2.816 39.0
The values of MAE obtained with full SCF are more consistent. What is not correct with 'Single shot' + ESM1?
Here is an example of input:
#
# Files Names
#
System.Name reference_scf_mae_t0_p0
level.of.stdout 1 # default=1 (1-3)
level.of.fileout 1 # default=1 (0-2)
DATA.PATH ./DFT_DATA19/
#
# Definition of Atomic Species
#
Species.Number 4
<Definition.of.Atomic.Species
Mg Mg7.0-s3p3d2 Mg_PBE19
O O5.0-s2p2d1 O_PBE19
Fe Fe6.0S-s3p3d2 Fe_PBE19S
Co Co6.0S-s2p2d2 Co_PBE19S
Definition.of.Atomic.Species>
#
# Lattice
#
Atoms.UnitVectors.Unit Ang # Ang|AU
<Atoms.UnitVectors
101.802950000000 0.000000000000 0.000000000000
0.000000000000 2.980000000000 0.000000000000
0.000000000000 0.000000000000 2.980000000000
Atoms.UnitVectors>
#
# Atoms
#
Atoms.Number 29
Atoms.SpeciesAndCoordinates.Unit FRAC # Ang|AU|FRAC
<Atoms.SpeciesAndCoordinates
1 Mg 0.216311823970 0.987251845638 0.987613624161 4.0 4.0 0.0 0.0 0.0 0.0 0
2 O 0.215975138245 0.486647852349 0.487097684564 3.0 3.0 0.0 0.0 0.0 0.0 0
3 O 0.237437895464 0.986885503356 0.987382449664 3.0 3.0 0.0 0.0 0.0 0.0 0
4 Mg 0.237377108424 0.486848288591 0.487336879195 4.0 4.0 0.0 0.0 0.0 0.0 0
5 Mg 0.258725323775 0.987473691275 0.987973087248 4.0 4.0 0.0 0.0 0.0 0.0 0
6 O 0.258723127375 0.487126677852 0.487404966443 3.0 3.0 0.0 0.0 0.0 0.0 0
7 O 0.280110440808 0.987547080537 0.987361979866 3.0 3.0 0.0 0.0 0.0 0.0 0
8 Mg 0.280102629639 0.487527751678 0.487319530201 4.0 4.0 0.0 0.0 0.0 0.0 0
9 Mg 0.301534913281 0.987804496644 0.987071342282 4.0 4.0 0.0 0.0 0.0 0.0 0
10 O 0.301542518169 0.487500033557 0.486949630872 3.0 3.0 0.0 0.0 0.0 0.0 0
11 O 0.322988712017 0.988155369128 0.987677382550 3.0 3.0 0.0 0.0 0.0 0.0 0
12 Mg 0.323000853118 0.488143724832 0.487500906040 4.0 4.0 0.0 0.0 0.0 0.0 0
13 Mg 0.344373820209 0.988879328859 0.988736677852 4.0 4.0 0.0 0.0 0.0 0.0 0
14 O 0.344469605252 0.488560805369 0.488321644295 3.0 3.0 0.0 0.0 0.0 0.0 0
15 O 0.365431819019 0.990134798658 0.989870604027 3.0 3.0 0.0 0.0 0.0 0.0 0
16 Mg 0.366339503914 0.489868926174 0.489587852349 4.0 4.0 0.0 0.0 0.0 0.0 0
17 Fe 0.385941287556 0.993088624161 0.992906677852 8.0 6.0 0.0 0.0 0.0 0.0 0
18 Co 0.396889946706 0.495171241611 0.494998859060 8.5 6.5 0.0 0.0 0.0 0.0 0
19 Fe 0.409242879504 0.996906912752 0.996917718121 8.0 6.0 0.0 0.0 0.0 0.0 0
20 Co 0.421590669033 0.497324798658 0.497312315436 8.5 6.5 0.0 0.0 0.0 0.0 0
21 Fe 0.433992182937 0.998191610738 0.998163288591 8.0 6.0 0.0 0.0 0.0 0.0 0
22 Co 0.446007438881 0.499414765101 0.499477617450 8.5 6.5 0.0 0.0 0.0 0.0 0
23 Fe 0.458024014039 0.998850570470 0.998888053691 8.0 6.0 0.0 0.0 0.0 0.0 0
24 Co 0.470293507212 0.500369865772 0.500308255034 8.5 6.5 0.0 0.0 0.0 0.0 0
25 Fe 0.482453824766 0.999777382550 0.999643221477 8.0 6.0 0.0 0.0 0.0 0.0 0
26 Co 0.494465542502 0.499818590604 0.499463154362 8.5 6.5 0.0 0.0 0.0 0.0 0
27 Fe 0.506956796438 0.999877684564 0.999746845638 8.0 6.0 0.0 0.0 0.0 0.0 0
28 Co 0.519460871223 0.499677953020 0.499358724832 8.5 6.5 0.0 0.0 0.0 0.0 0
29 Fe 0.529706501629 0.999559966443 0.999872080537 8.0 6.0 0.0 0.0 0.0 0.0 0
Atoms.SpeciesAndCoordinates>
#
# SCF
#
scf.Electric.Field 0.0 0.0 0.0
scf.Kgrid 1 25 25
scf.XcType GGA-PBE
scf.SpinOrbit.Coupling on
scf.SpinPolarization NC
scf.energycutoff 600
scf.ElectronicTemperature 900
scf.maxIter 1000
scf.EigenvalueSolver Band
scf.Mixing.Type Rmm-Diish
scf.criterion 1e-08
scf.restart on
scf.partialCoreCorrection on
scf.Mixing.History 60
scf.Mixing.StartPulay 40
scf.Init.Mixing.Weight 0.3
scf.Min.Mixing.Weight 0.001
scf.Max.Mixing.Weight 0.4
scf.lapack.dste dstevx
scf.Mixing.EveryPulay 1
scf.fixed.grid 0.0 0.0 0.0
scf.stress.tensor off
#
# MD
#
MD.Type Nomd
MD.maxIter 1
#
# ESM
#
ESM.switch on1
ESM.buffer.range 75.0
ESM.potential.diff 0.0
ESM.direction x
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