I am studying point defects in hBN using Quantum ESPRESSO. It is not clear if electron spin-spin interactions are typically/can be included in DFT calculations. I understand that spin-orbit interactions can be included in the calculation by performing a noncollinear calculation with lspinorb = .true.. I have also found some papers which discuss zero-field-splitting, but cannot find much information about magnetic dipole-dipole interactions. It would make sense to me if the interaction was included in the functional, but it appears that only the Coulomb interaction is considered (I am using the HSE functional). Perhaps spin-polarized calculations somehow include the spin-spin interaction?
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No. Magnetic dipole interactions are not included in DFT. In solids, this effect is usually very weak. If you want to calculate it, you can just solve the contribution to the Hamiltonian analytically. Just write a code which takes in the moment, distances between magnetic atoms in expression 1 (https://en.wikipedia.org/wiki/Magnetic_dipole%E2%80%93dipole_interaction).
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$\begingroup$ Excellent- thank you. Would you happen know of any papers which discuss this topic? $\endgroup$– KenCommented Apr 9, 2021 at 22:48
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$\begingroup$ The references in Wikipedia should be a start. If you are dealing with Crystals (solids), this effect should be to the tune of 10^-6 to 10^-7 eV. What kind of references are you looking for? The analytical stuff should be in the Wikipedia link and some physics textbooks. With regard to the calculations for magnetic solids, I've seen papers mention this calculated value, but they typically don't specify anything else, since there is nothing besides the equation IMO. $\endgroup$– Xivi76Commented Apr 9, 2021 at 23:21
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$\begingroup$ I just thought there might be some research that has dug a little deeper into this subject. I find it strange that hyperfine interactions are often considered in DFT calculations but not spin-spin. I am studying point defects in solids and it seems common for group theory methods to consider (in order) Coulombic, spin-orbit, spin-spin, and hyperfine interactions. I was expecting a similar sort of analysis in DFT calculations. $\endgroup$– KenCommented Apr 11, 2021 at 0:08
codeblock, and please say "hello" at least once in the Quantum ESPRESSO chat room!. $\endgroup$