Figure9

Figure 9. Temperature dependence of $$\mathrm{\Delta }{C_2}^{\ast }$$ (squares) and best fit using the correlated Einstein model (dashed line), which gives $${\nu }_{\parallel }=13.1$$ THz and a constant shift $$|a_{\parallel }|=0.0036$$Å$${}^2$$. Circles and solid line are, respectively, the resulting parallel MSRD and the corresponding Einstein model. Error bars have been omitted for clarity.