Fig. 2. Crystal structure and the results of DFT phonon calculations for the cP8-Y₄H₂₃ yttrium hydride.

(A) Compound’s unit cell, with the Y atoms shown as green and hydrogen atoms as light pink balls. (B) Coordination environment of the Y1 and Y2 atoms in Y₄H₂₃. (C) Phonon dispersion curves along high-symmetry directions in the Brillouin zone and phonon density of states for Y₄H₂₃ calculated at 138 GPa.