图7. 不同温度下总振动均方位移$\mbox{vMSD}\left( {\Delta r^2} \right)$和方向解耦的$\mbox{vMSD}\left( {\Delta x^2,\Delta y^2,\Delta z^2} \right)$的空间自关联函数. 方形符号代表任意方向$\Delta r^2=\Delta x^2+\Delta y^2+\Delta z^2$总振动均方位移的空间自关联函数$C_{\Delta r^2} \left( r \right)$,而圆形符号则代表3个特定方向$\Delta x^2$, $\Delta y^2$, $\Delta z^2$均方位移空间自关联函数的平均值$C_{\Delta x^2,\Delta y^2,\Delta z^2} \left( r \right)$

Fig.7. The spatial autocorrelation function of total vibrational MSD ($\Delta r^2)$ and directional resolved vibrational MSDs ($\Delta x^2,\Delta y^2,\Delta z^2)$ at different temperatures. The squares denote the correlation function $C_{\Delta r^2} \left( r \right)$ of total vibration MSD in any direction, i.e. $\Delta r^2=\Delta x^2+$\\ $\Delta y^2+\Delta z^2$. And circle stand for the correlation functions $C_{\Delta x^2,\Delta y^2,\Delta z^2} \left( r \right)$ for the directional MSDs $\Delta x^2$, $\Delta y^2$, and $\Delta z^2$, respectively