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Magnetic dipole-dipole interaction and crystal field splitting
Posted: Wed Mar 06, 2024 5:58 am
by hongyang_ma
Dear VASP users,
I was wondering if VASP has the capability to compute the magnetic dipole-dipole interaction and crystal field splitting energy of a solid system?
Regards,
Hongyang
Re: Magnetic dipole-dipole interaction and crystal field splitting
Posted: Wed Mar 06, 2024 9:37 am
by merzuk.kaltak
Dear Hongyang,
yes VASP can calculate the crystal field splitting energy in solids.
This energy is typically estimated from the density of states of the system with the broken symmetry.
For instance following example is taken from
a study on silver doped hollandite
For convenience, here is Fig. 6 from the paper:
pDosAg2Mn8O16.png
The blue and green lines show the dx2-y2 and dz2 states of the Mn in the purple octahedra.
In the high-symmetry case these two states represent the e_g states of Mn in the purple octahedra, see Fig. (c), where both peaks are very close to each other.
To good approximation, there is no crystal field splitting present.
Fig. (d) shows the DOS after doping the material with Ag and applying a specific U-value.
The symmetry of the e_g states is now broken, dz2 and d_x2-y2 peaks are now well separated.
The energy difference of the corresponding blue and green peak in Fig. (d) is the crystal field splitting after the Jahn-Teller distortion and is roughly 2 eV.
Re: Magnetic dipole-dipole interaction and crystal field splitting
Posted: Wed Mar 06, 2024 10:15 pm
by hongyang_ma
Dear Merzuk,
Thank you for your response. It has been quite helpful.
Regarding the computation of magnetic dipole-dipole interaction energy, does VASP have the capability to handle this task? If not, could you recommend a post-processing code or method that can perform this calculation?
Regards,
Hongyang
Re: Magnetic dipole-dipole interaction and crystal field splitting
Posted: Thu Mar 07, 2024 8:53 am
by merzuk.kaltak
Dear Hongyang,
here is a study on
magnetic dipole-dipole interaction using magnetic density from first principles.
Looking at Eq. (1) the
atomic spin moment model (AMM) gives an estimate for the magnetic dipole-dipole interaction via
AMM.png
To evaluate this expression, you require the positions of the atoms
R_j from the POSCAR and their magnetic moments
m_i.
The magnetic moments can be found in the OUTCAR after an
ISPIN=2 calculation.
Look for following lines.
Code: Select all
magnetization (x)
# of ion s p d tot
------------------------------------------
1 0.006 -0.003 1.702 1.705
2 -0.006 0.003 -1.702 -1.705
3 0.000 0.000 0.000 0.000
4 0.000 0.000 0.000 0.000
Be aware that the energies in vasp in eV.
Re: Magnetic dipole-dipole interaction and crystal field splitting
Posted: Thu Mar 07, 2024 11:55 pm
by hongyang_ma
Dear Merzuk,
Great! Thanks a lot!
Regards,
Hongyang
Re: Magnetic dipole-dipole interaction and crystal field splitting
Posted: Tue Mar 26, 2024 5:24 am
by hongyang_ma
Dear Merzuk,
I'm curious if this method also applies to rare earth elements like Er for investigating the crystal field splitting energy of its 4f orbitals.
Regards,
Hongyang
merzuk.kaltak wrote: ↑Wed Mar 06, 2024 9:37 am
Dear Hongyang,
yes VASP can calculate the crystal field splitting energy in solids.
This energy is typically estimated from the density of states of the system with the broken symmetry.
For instance following example is taken from
a study on silver doped hollandite
For convenience, here is Fig. 6 from the paper:
pDosAg2Mn8O16.png
The blue and green lines show the dx2-y2 and dz2 states of the Mn in the purple octahedra.
In the high-symmetry case these two states represent the e_g states of Mn in the purple octahedra, see Fig. (c), where both peaks are very close to each other.
To good approximation, there is no crystal field splitting present.
Fig. (d) shows the DOS after doping the material with Ag and applying a specific U-value.
The symmetry of the e_g states is now broken, dz2 and d_x2-y2 peaks are now well separated.
The energy difference of the corresponding blue and green peak in Fig. (d) is the crystal field splitting after the Jahn-Teller distortion and is roughly 2 eV.