Density functional perturbation theory for lattice dynamics with fully relativistic ultrasoft pseudopotentials: the magnetic case

We discuss the extension of density functional perturbation theory for lattice
dynamics with fully relativistic ultrasoft pseudopotentials to magnetic materials [1].
We avoid the computation of the response at -q by using explicitly the
time-reversal operator, which is applied to the Sternheimer linear system and to its
self-consistent solutions, an approach that has been introduced for the calculation
of magnons [2].
We validate our implementation by comparison with the frozen phonon method in fcc Ni
and in a monatomic ferromagnetic Pt wire, and present an application to MnBi.
We are working to extend the technique to the computation of the phonon dispersions
of magnetic polar insulators.

References:

[1] A. Urru and A. Dal Corso, Phys. Rev. B 100, 045115 (2019).
[2] T. Gorni, I. Timrov, and S. Baroni, Eur. Phys. J. B 91, 249 (2018).