Fig. 3.

Phonon DOS from experiments and simulations. ($A$) INS powder measurements at the ARCS with ${\mathrm{E}}_i=20$ and 80 meV to get fine resolution at the low-energy portion and the whole spectrum. Data are stitched together at 9 meV. Blue, green, orange, and red lines are measured at 300, 450, 520, and 650 K, respectively. ($B$) Calculated neutron-weighted DOS. Black dashed line is labeled as DFT, and AIMD at 300 and 600 K are blue and red dashed lines, respectively. ($C$ and D) Site-projected DOS from DFT for the $c$-axis polarized (C) and in-plane ($D$) motions in the $a$–$b$ plane. Ag motions mainly contribute the strong peak around 3.5 meV for the in-plane vibration and a weaker peak near 10 meV for $c$ polarizations.