## Magnetism

Magnetic properties are of interest from both fundamental and application perspectives; atomistic spin dynamics protocols are being used to extend the DFT data of the OMDB.

A magnetic system can be described in its more general form by the spin Hamiltonian:

$$ \mathcal{H}_{\mathrm{M}} = -\frac{1}{2}\sum_{i,j} \mathcal{J}_{ij}^{\alpha\beta} S_i^{\alpha} S_j^{\beta} - g_e \mu_B B^{\alpha} \sum_{i} S_i^{\alpha} $$

Using ab initio methods to solve this Hamiltonian gives us information about the dispersion relation \(E(\boldsymbol{k})\), and the dynamical structure factor \(S(\boldsymbol{Q}, \omega)\), measured in inelastic neutron scattering experiments.

A central activity for us in Stockholm is the work we pursue to extend the Organic Materials Database (OMDB) to include magnetic excitation spectra. Current work is extending the OMDB to include magnetic excitation properties. For inelastic neutron scattering we focus on the dynamical structure factor \(S(Q, ω)\) which contains information on the excitation modes of the material. We introduce a new dataset containing atomic magnetic moments and Heisenberg exchange parameters for which we calculate the spin wave spectra and dynamic structure factor with linear spin wave theory and atomistic spin dynamics.