How can we calculate curie temperature through vasp calculations?
Anyone can suggest how to initiate Monte Carlo simulations for curie temperature calculations for comparison?
One method for calculating the Curie temperature of a ferromagnetic using density functional theory is to construct model spin Hamiltonian to treat in terms of a mean-field type approach (in this case the Curie Weiss model). The model will be parameterized by J, the exchange constant between magnetic atoms (with different J's for 1st nearest neighbors, 2nd nearest neighbors, etc). Essentially in this step, you would need to do DFT calculations for a variety of magnetic configurations and then use the energies to extract the values of J. An example of this was done in the following paper for EuO and Gd-doped EuO:
J. Lee, N. Sai, and A. A. Demkov "Spin-polarized two-dimensional electron gas through electrostatic doping in LaAlO3/EuO heterostructures," Phys. Rev. B 82, 235305 (2010)
A more detailed description of how to construct the effective Hamiltonian and use DFT to extract the parameters can be found in Jaekwang Lee's dissertation in Chapter 5 (in particular sections 5.4.6 through 5.4.8 (p58-p64)). The dissertation is available from the University of Texas here:
https://repositories.lib.utexas.edu/handle/2152/ETD-UT-2010-08-2012
Dear@Dr. Andrew
How does confirm type of magnetism ferro, antiferro etc. from density functional theory (using VASP code)?
How does report bandgap for spin polarized calculation ?
In spin polarized calculation we get two bandgaps one for spin up and other for spin-down. Both have different bandgap values and experimentally we have only one bandgap value. What should be the exact value of bandgap for spin polarized calculations. For example we want to see trend in bandgap increasing or decreasing by dopant in case of spin polarized calculation.
Thank You
Shilendra
To get particular magnetic configuration, you should build a supercell if your unitcell is not big enough. Then, you should set ISPIN=2 and set up MAGMOM for each atom in your supercell/unit cell. You will not do energy minimization since VASP optimizes magnetic moments. All you need to do is single point energy calculation with fixed initial local magnetic moments.
If you want to get band gap, you should put both band structures or density of state of up and down-spins together.
Kien Nguyen Cong Hi! Could you please explain a little bit more on the magnetic configurations? If a supercell contains 2 species and 8 atoms (50-50%), how can we describe antiferromagnetic configuration? If we relate Tc to the energy difference between E_FM and E_AFM, then which AFM configuration should be chosen if multiple configurations are available?
Thank you very much!
Dear Dongsheng Wen . Please see this tutorial: https://pythonhosted.org/pychemia/tutorial.magnetic_moments.html
For both FM or AFM configurations, one with lowest energy is ground state. However, I think you need multi configurations to solve linear equations.
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