# Are electron dipolar spin-spin interactions included in DFT calculations?

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?

• +1. Welcome to the site and thank you so much for contributing your question here! We hope to see much more of you in the future!! Please take a look at the edit I made for your code block, and please say "hello" at least once in the Quantum ESPRESSO chat room!. Apr 9 at 5:00
• Thanks for the comment Nike!
– Ken
Apr 9 at 5:08

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).

• Excellent- thank you. Would you happen know of any papers which discuss this topic?
– Ken
Apr 9 at 22:48
• 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. Apr 9 at 23:21
• 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.
– Ken
Apr 11 at 0:08