Fig. 4.

Pressure dependence of the effective environmental force constant k_eff for dynamics on the τ = 1 ps time scale derived by using linear fits to 〈Δr²〉_P(T) in the harmonic regime (T ≤ 160 K), as illustrated in Fig. 3. The solid and dashed lines are linear fits in the ranges P ≤ 400 MPa and P ≥ 700: MPa.