In this tutorial we demonstrate the same total energy method to calculate exchange parameters for the same system KCuF3 [1] but with using of full-potential Wien2k code. As in the previous case we choose U = 7.6 eV and JH = 1 eV.

To perform GGA+U calculation with Wien2k one needs jass.inp, сase.struct, сase.inorb and сase.indm. All these files you can find in tutorial archive. With the aim of calculation more then one exchange parameter we made the supercell containing 4 Cu ions.

The jass.inp of the calculation is:

[main]
code = wien2k
ncore = 4
[DFT]
mode = auto
method = energies
S = 0.5
magion = Cu

Having all calculations finished we investigate the jass.out, which gives us values of three exchange integrals J0 = 37.2 meV (AFM), J1 = −0.5 meV (FM) and J1 = 1.2 meV (AFM) corresponding to nearest neighbours (3.93 Å), next nearest neighbours (4.15 Å) and next next nearest neighbours (5.72 Å). These values are in good agreement with experimental data taking into account the difference in Heisenberg model formulation.

 

1. S. V. Streltsov and D. I. Khomskii, Physics-Uspekhi 60, 1121 (2017)

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