Magnetic Exciations in TDDFT with GGA kernel

In ordered magnets of all forms (ferromagnets, antiferromagents, ferrimagnets, etc.) we encounter wave like excitations that propagate through the lattice of ordered spins. Correctly predicting these collective excitation modes is essential for understanding the thermodynamic properties of such materials. Theoretically, TDDFT within the linear regime, can successfully capture these low energy spin waves. However, it requires an approximation to the exchange-correlation (XC) kernel, which encapsulates the electron-electron interactions of the many-body systems. Despite the plethora of approximations for the XC energy functional, only the ALDA kernel has been implemented and applied to study these magnetic excitations. In the work presented here we climb up the Jacob’s ladder of functionals and derive the XC kernel for GGA functionals. This is then tested by calculating the magnon spectra for simple ferromagnets and Heusler ferrimagnets using the PBE GGA functional.