Animations of vibrational bands

The IR spectra of alpha-Na(bim) (https://doi.org/10.1021/acs.cgd.4c00927) were calculated using the Vienna Ab Initio Simulation Package (VASP, version 5.4), using periodic density functional (DFT) with the optPBE-vdw functional and projected augmented wave (PAW) pseudo-potentials. The IR calculations are based on a geometry-optimized structure, which included both the relaxation of the cell parameters as well as the relaxation of the nuclei position. The cut-off energy of the plane wave basis set is 400 eV. For describing the electronic states, the Methfessel-Paxton smearing method was employed with a smearing width of 0.2 eV. The convergence criteria for the forces on the nuclei was 0.02 eV/Å and the criterion for the electronic relaxation is set to 10^-7 eV. The Brillouin zone integration is based on a 6x6x1 k-point grid.

The optimised lattice constants of the used unit cell are a = 8.2672 Å, b = 7.0732 Å, and c = 11.3000 Å. The IR calculations were carried out using the density functional perturbation theory (DFPT) vibrational analysis approach.