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I am new to density functional theory. My goal is to calculate magnetic anisotropy energy using the force theorem. For that, I have been told that one can run a self-consistent calculation with some magnetic moment orientation, and then using the same charge density, calculate (using a non-self consistent calculation) the energy of a different magnetic orientation. The difference between these two energies can yield the magnetic anisotropy energy.

I also heard that the latter is called a "single-shot" calculation as it does not have to go through the self-consistent iteration procedure. Can you kindly comment on whether my understanding here is correct or not?

Please help. Thank you.

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1 Answer 1

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"Single shot" can mean different things in electronic structure. It just depends on what is held constant.

What you refer to is evaluating the Kohn-Sham energy with fixed spatial orbitals, but for different spin states. This will give you non-variational energies for the other spin states, while the reference spin state is favored as the orbitals are optimal for it.

It is also commonly used for the self-consistent evaluation of the electronic energy for a fixed nuclear geometry. For instance, you might optimize the geometry with a cheaper method like tight-binding density functional theory (DFT), and then run a higher-level calculation like Kohn-Sham DFT on that geometry. In quantum chemistry, one often obtains geometries with DFT and uses more sophisticated (and much more expensive) methods like coupled-cluster theory to obtain reliable total energies for these fixed geometries.

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