Compound 1 is a monometallic Dy(III) molecule with a pentagonal bipyramidal coordination geometry. The molecule crystallises in the orthorhombic space group C2221 with half a molecule in the asymmetric unit and two complete molecules in the conventional unit cell (Figure ). Optimisation of the crystal structure of 1 with periodic DFT yields a very similar structure to the experimental one used as the starting point, with optimised unit cell parameters very similar to the measured values (Table ), and an RMSD for all atomic positions of 0.10 Å. The low-energy phonon dispersion (Figure ) comprises the three acoustic modes, corresponding to rigid translations with zero energy at the Γ-point, and a high density of dispersive pseudo-acoustic modes that arise predominantly from combinations of rigid molecular translations and rotations. The DoS shows a high-density continuum of phonon modes below ca. 250 cm -1 (Figure ), while the complete spectrum extends up to 3500 cm -1 and at higher frequencies comprises relatively flat bands of intramolecular modes (Figure ).